In version 4.0 to 4. default character was called “MyCharacter”. In 4.7 they’ve been renamed to “ThirdPersonCharacter” or the name of the template + character.
Search in the blueprint folder for your character or look it up in your gamemode. You have to use that name instead of “MyCharacter”.
Here are the two examples of how it should look like:
Possess is a function of the controller. You have to drag off of a “Get Controller” node and search for “Possess” then you can run that function from the character blueprint.