Hey Marina, first of all: awesome job on your latest entry. Looking real good =) Working on that same assignment this evening, haha! About your question: I'm not an expert on what is the best way to hold it, but I'd say just experiment with it and find what works for you. I'm currently using a display tablet, but when I was using my intuos I just held it right in front of me, looking at the monitor.
Also don't worry too much about those lines! If it's not working yet, keep trying! Also practice it on paper if possible =) It's basically the same exercise where you train using your entire arm for practicing dexterity. Just keep practicing and maybe see it as a daily warm-up routine of 10-15 minutes before you draw?
I wish you all the best with the following assignments and looking forward to seeing them =) Good luck!