Hello and welcome to KH! It's great that you've been able to learn to knit from the internet, you must be very determined.
Well, I hope I can explain this clearly enough, please ask questions if you need further clarification.
To knit the ‘long stitch’, hold your knitting as you normally would, and stretch it out, this will help you identify the correct stitch. You will be inserting your right needle into the ‘leg’ of the stitch that is two stitches directly below the stitch on your left needle.
Pull this stitch up and onto your right needle, and then transfer it to your left needle. The two stitches that are above this stitch will drop down; don’t be surprised, they are supposed to do this. You are now ready to knit the stitch from two rows below to form a ‘long stitch’.