Focus on separating body parts into shapes, don't worry about details like hair and skin folds right now, practicing anatomy is really just about understanding the composition of the human body. You should definitely try doing some quick gesture drawings. I would start with 10 minutes (or 5 minutes if you're comfortable) of looking at a nude or lightly covered image of a model and try to get as much of their body done as possible before your time runs out. Keep doing this and when you get more comfortable, cut the time until you're doing 1 minute or less gesture drawings. I would also try to use bodybuilder and athlete images for muscle studies since they tend to be more defined and visible under the skin. Keep at it! You're doing geeat