Here are the completed sentences with the First Conditional:
1) If I am not (not/be) busy, I will come (come) with you.
2) If it rains (rain), we will stay (stay) at home.
3) I will call (call) you if I have (have) time.
4) If she doesn't study (not/study) hard, she will not pass (not/pass) the test.
5) If the weather is (be) nice, we will go (go) to the beach.
6) You will get (get) fat if you don't stop (not/stop) eating so much.
7) If I see (see) John, I will tell (tell) him about the party.
8) Mum will be (be) very angry if I don't tidy (not/tidy) my room.
9) If we don't leave (not/leave) now, we will miss (miss) the bus.
10) You will not do (not/do) your homework if you don't go (not/go) to the party.
**Explanation:** First Conditional is about a possible future. Structure is: If + Present Simple, will + verb.