Should i add both income amounts togeter for me and my husband under letter 6475?

Yes.    You are being asked if you received the total amount that the two of you should have received.   The 3rd EIP was $1400 per person.   A married couple would have received $2800, and $1400 per dependent if you had any dependents.  Most often, the IRS divided your total in half and sent a letter for half to each spouse.   If you received the total amount that you were supposed to get then by the time your tax return is filled out your line 30 should be blank.   Or if you have a new dependent, there should be an amount on line 30 for the new dependent.

PREVIEW 1040

https://ttlc.intuit.com/questions/1901539-how-do-i-preview-my-turbotax-online-return-before-filing

Click on Tax Tools on the left side of the screen. Click on Tools. Click on View Tax Summary. Click on Preview my 1040 on the left side of the screen.