The first is through PMs, or your Game Mail. Some people may advertise looking for a PM roleplay partner on the forums or in the chatboxes, so you can find roleplay partners there.

The second is through the Scenes, accessed by Roleplay > Group Roleplay. There are three Scenes in Group Roleplay: Scene 1, Wolf Pack Life; Scene 2, The Free Range; and Scene 3, Unexplored Territory. Scene 1 is more realistic and strictly wolves-only. Scene 2 allows for wolf and human interaction. Scene 3 is anything goes, as long as it's appropriate and abides game rules.

The first is on the Roleplay board of the forums: https://wolfplaygame.com/forums.php?f=15

Roleplays here are thread-based, so you can find a roleplay that best suits you. There are also five sub-categories on the board to choose from: Realistic, Fantasy, Literate, Semi-Literate and 1x1.