Help! I have no idea how to come up with a subplot!

Does anyone have ay advice on how to come up with a subplot? I need one, but I have no idea where to start.

Here are a few prompts off tumblr!

My other advice would be focusing on characters other than the main ones. It adds more realism and depth to the story if everyone around the protagonist is also dealing with their own personal stuff along the way

Thanks! :)