I can't find out/figure out how to use this app.

[optimistic pessimist]

1. I can't figure out how to use this app.
2. I can't find out how to use this app.

I think the use of "figure out" in #1 is correct.
Is the use of "find out" in #2 also correct?

 

[emsr2d2]

They're both possible but with different meanings.
If you use "figure out", it suggests that you've tried various methods that you came up with on your own but none of them worked. Using "work out" would have much the same meaning.
If you use "find out", it suggests you're looking elsewhere (such as on the net) for instructions but you haven't found any. It would be more natural as "I haven't been able to find out how to use this app".