The comfort will come in time as your legs adjust to being able to sit like that. Try sticking a pillow under your butt. This will help keep your back straight with your legs crossed and will reduce the numbness you feel. In terms of meditation, there are a variety of things you can do. When first starting out, a good goal is increased concentration. Counting your breath without your mind wandering or following your breath are good places to start.
There are also a variety of visualization techniques you can use, such as imagining good air coming in with your inhale, and bad air coming out. For example, make the good air a bright color you like and the bad air, darker of the same shade. Visualization helps, because the more of your mind that is focused on the task at hand, the less room there is for other thoughts to wander in. Personally i like visualization becuase to me it is more interesting then counting, and doesnt get as boring. The downside i've found to counting (maybe this is just my weakness) is that if i establish a goal, i get tied to it. For example, i'm going to meditate for 100 breaths, around 37 or so, i'm like man i have 63 more breaths to go and lose focus because i become aware of time. By focusing on the moment and not envisioning any goals, i was able to make much more progress. Hope this helps