How to e-file income tax when u have form 16?

I'm into service and would like to know how to file tax online when i have form 16.

Tax has already been deducted by company.

I searched on google but i want a tutorial which is easy to understand and full proof as i have heard that u cannot change the filled form if u r filing after july 31st.

how much do i have to pay for efiling?

please help.