How much amount, monthly total or yearly total, should i enter in my income?

All income to be reported on a tax return is the annual amount.

You would enter the total income you received for the year in each category.  For example, if you had a business, then in the business income section you would enter your total business income for the year.  

If you had a job, your W-2 includes your total income for the year.

Any interest you received for the year or any type of other income will all be entered as the yearly total.