I'm making a first person shooter game. How do I make a reload animation?

I’m using the default skeletons and everything. This must be a dumb question, so I’m very sorry.

Are you asking how to create a new animation or how to use existing animations to setup a character controller? If you want to know how to make a controller, you should check the shooter demo in the learn tab of the launcher. They cover just about every system you need to make a first person shooter. You can also get some basic fps animations from that project for your own use.

You can only make rudimentary new animations in the Unreal Editor. To make something more complex you need a digital content creation app like Blender or Maya. You can export your character to an external program like that and make your animation there. In addition to the default skeleton you will also need a proper animation rig.