I need to amend my return but I already received the refund. I can still amend it, correct?

Yes, you can amend a return if you have already received a Federal refund from the original filed return.  In fact, it's recommended for people to wait until they do receive the refund before amending the return.  When you go through the amending process, it will figure out if you receive additional refund, have to pay any back, or no change.

FAQ:  Does amending my return affect my refund?

https://ttlc.intuit.com/turbotax-support/en-us/help-article/tax-return/amend-already-received-refund/L4AOMgAu4_US_en_US

TurboTax article on amending a return

https://turbotax.intuit.com/tax-tips/amend-return/how-to-file-an-amended-return-with-the-irs/L6kO691J8

NOTE:  Before attempting to amend the return, if you are using Online TurboTax,  I would download a backup copy of the original return's full PDF with worksheets and the *.tax2024 data file.  You would then have the original data just in case something goes wrong with the amending process.   Be sure to store all PDF's and tax data files safely and securely, since they have a lot of personal and financial information.

     If you are using desktop software, then in addition to a PDF make a backup copy of the original *.tax2024 data file before amending and store the files somewhere safe and secure. 

    Label the backup files in a way to distinguish them as "original" or some term so that you don't later get them mixed up.

In Online TurboTax to get the full PDF with worksheets, go to the Tax Home and look for a link "Add a State".   That doesn't really add one, but will open the return interview back up.   Then when the return interview is opened back up, go to the left menu column and click on TAX TOOLS, then PRINT CENTER.   Then choose "View/print/download" this year's return.   You will have some options to choose just the return, or the return and TurboTax worksheets, or return with all worksheets.

Do not make any changes while you are back in the return interview using "Add a State."   The amending process has to start off with the return as originally filed.  Only make the changes when instructed after you begin the amending process.