Ok, I was thinking it might have been a kit that came with a specific pattern and thread for said pattern. I know you said you understand the concepts, but here are my general "getting started" tips:
-Try to start with a high count of aida. The "count" is based off how many blocks per inch - the smaller the number, the easier it is to see the holes, etc. 14ct is a good starting point, 16ct is OK, 18ct is not a good starting point. I wouldn't recommend trying to learn on linen. Aida is easy!
-Most patterns have a cross section showing the middle of the design. When learning, it might be easist to find the middle of your design, the middle of your fabric, and start there. To find the middle of your fabric, fold in half, and in half again, making a deep crease. Boom, middle. If the fabric is too soft to maintain a crease, you can throw your needle in the fabric to hold the place while you hoop it.
-Hoops. Pretty self explanatory. Some people like to stitch in-hand without hoops, but I like fabric tension. You want your fabric taught, but not TOO tight. Wooden hoops are the standard, but there are also nifty plastic hoops (easier on hands, no splinters) and snap together plastic square hoops called q-snaps. Scroll frames also exist but are pretty advanced and expensive and used for huge projects. I like round hoops or q-snaps.
-Dividing your floss. Most skeins of embroidery thread consist of 6 strands and you're not meant to stitch with all 6 at a time. There are general recommendations based on your size of fabric and how dense you want your stitches. I like to stitch with 2 strands on 14ct or 16ct which is what I use most often. Some patterns have recommendations on how much to use. You might see "Stitch 2 over 1" which means stitch with two strands over one square. Two over two would be two strands over two squares, usually if you are stitching on linen or something really high like 32ct cloth. To divide your floss, you'll want to hold the skein and pull out a few lengths, and cut the floss (not too long, it will be prone to tangling if it's too long, I like to do the length from my hand to my shoulder). Once you have a length of trimmed floss, pull one or two strands straight up to remove from the rest.
This is a good video showing what I'm talking about (but ignore the thread conditioner, you don't need that unless you are using metallic thread or something vintage that knots easily). Put the rest of the threads aside for now.
-Needles There are recommended sizes to use per fabric count, but I generally use size 22 needles for 14 or 16 ct. You might need a smaller needle if it's making a "popping" noise or if it's hard to guide through the fabric. You want embroidery or tapestry needles, not sewing needles, because you will stab yourself and bleed on your project.
-Starting. I like the loop start method, and I highly recommend learning it before you get in the habit of knotting your thread.
This video shows it done really well. Knotting isn't the WORST thing in the world, but it can make the back bumpy and be harder to frame. Some people will say never ever ever ever knot your thread, but fuck it, sometimes it's just easier. There is also pin stitch and waste knots, but honestly, loop start or bust. It's so easy and quick.
-Reading your pattern. Some patterns just have colored in blocks, some have symbols, some have both. There should be a key showing what color corresponds to what symbol. If any symbols are smaller on your pattern, or sharing a space with another symbol, those are fractional stitches. There are full stitches (standard full X) and also quarter stitches, half stitches, and three quarter stitches.
This video reviews fractional stitches really well.
-Gridding. If you're losing count or REALLY struggling, grid your fabric. I recommend a water soluble marker and a ruler. Most patterns are gridded every 10 squares and you can grid your fabric every 10 squares, that way you never have to count higher than 10 and you can work one block at a time. People do this for larger projects, but I think it would be great for a beginner too.
This video is way too long, but skip around and you'll get the gist.
-Ending your thread. I like to run my thread under completed stitches along the back to end a color. Again, knotting isn't great. I've actually had knots pull through to the front when not ran under nearby stitches.
This video shows it very well.
Accessories you probably don't need but worth mentioning:
-Needle threader - I used to lick my thread, but now I can't live without my needle threader
-Needle minder - basically a decorative magnet you can stick your needle to while stitching or changing thread. Don't put the needle in your mouth!
-Grime guard - Fabric piece that goes around the edges of your hoop to protect your work from grubby hands. I use dollar store fabric steering wheel covers
-Stitch rippers - for those unfortunate accidents.