First, transitions are easier to do in premiere Pro. After Effects is better suited to creating individual effects shots and on occasion short sequences. There are several wipe transitions included in AE. You can also use gradient wipes, animate masks, use other layers for track mattes, or a bunch of other options. This is all real basic stuff. I would suggest that you type "Transition wipe" in the search help field at the top right corner of AE and follow some of the links.