Alright, so the frog is very cute, hanging there. But there is a more figurative meaning to these words! Hang in there means, don’t give up; keep at it.
For example, imagine you have a friend who is going through a difficult period in his or her life. You can say to them: hang in there, it’ll get better soon, you’ll see.
Or, you’ve just witnessed a friend of your friend mess up, you can say, hang in there.
It’s just a colloquial way of telling someone not to give up, things will look up soon.