Mix in the yeast, then switch to the dough hook (if using a mixer) and start adding your flour in increments.
You want to add enough flour so that your dough doesn’t stick to the side of the bowl, but is still very soft and slightly sticky to the touch. If your dough looks like this, it is too sticky:
If your dough looks like this, it is just right. (Sorry the dough at the top is blurry. Just notice how it is not sticking to the side of the bowl):
Now let your dough rest for about ten minutes while you prepare the filling. Don’t worry about greasing the bowl or covering it or anything. The dough will be fine.