documents

First of all you didnt mentioned the category of thr assessee. if it is personal (salarised) person than following documets are basic to file the return
1. Form 16
2. Investment proof
3. Downloaded 26AS
4. Login ID and password.
5. other deductuon / invesment proof not covered under form 16
6. Bank statements
7. share trading p&l
8. linked aadhar card

IF YOU ARE FILING RETURN FOR FIRST TIME, THAN

FIRSTLY, REGISTER YOURSELF ON E-FILING INCOME TAX
THAN, VIEW 26AS FOR PREPARING YOUR RETURN
FILL THE DETAILS OF INCOME UNDER THE RESPECTIVE 5 HEADS UNDER WHICH YOU ARE LIABLE FOR PAYING TAX