Hi,
1. Please return it after use.
2. Please return it after using.
3. Please return it after usage.
Say it as in #1, in which 'use' is a noun'.
For #2, you'd have to say Please return it after using it, which is rather repetitive, although this is how we normally say it in everyday speech.
In #3, 'usage' is not an appropriate noun, 'use' is better.
Best wishes, Clive