Hello!
To contrive his theory, Wegener used the following pieces of evidence:
*Fossils - Animals whose fossils seemed to be more adapted to a certain climate were found in a different one. This suggests that all of the continents were once together.
* Puzzle (jigsaw) fit - The pieces of the continents that now remain seem to be able to connect almost perfectly.
*Tectonics - When some geographical aspects of the continents are analyzed together, it can be discovered that a continuous tectonic structure perfectly crosses each continent.
There are more, of course, but these are the more notable pieces of evidence (and all I could remember, heh). If you'd like me to elaborate on anything, just leave a comment down below and I will gladly help you!
I hope I helped! :)