I prepared my filing last night but i forget a supplemental income that i had for 3 months. how do i add it now?

Did you e-file already?  If you did NOT e-file yet you can still add information.   Click Add a State to get the software to let you back in to make changes.

BUT if you already e-filed, you cannot make any changes now.  If you e-filed, your return is in pending.

MY RETURN IS IN PENDING—what does that mean?

Did you e-file?  Did you click that big orange button that said “Transmit my returns now?”  If so, your return is now in “pending” on a server.  Do not try to change anything while your return is in pending.On January  23 the IRS will begin to accept/reject e-files.   Watch your emails—including your spam folder—for the notice about whether your e-file has been accepted or rejected.  If your return is rejected you will be able to make corrections before re-filing.   If the return you e-filed is accepted you will have to wait until it has been fully processed and then amend it to fix any mistakes or omissions.  It has been taking the IRS six to nine months—sometimes longer—to process amended returns.   If you e-filed your state return there will be another email later that tells you if the state was accepted or rejected.

WARNING:   Do not try to change anything on your return while it is pending.

https://www.irs.gov/newsroom/irs-sets-january-23-as-official-start-to-2023-tax-filing-season-more-help-available-for-taxpayers-this-year