If your return has been fully processed, then you need to do an amended return to add your SS benefits.  If your original return has not been fully processed, you need to wait.  The IRS may contact you about the missing SS benefits.  Since SS benefits are taxed I don't think it would increase your refund, unless you had taxes taken out, then maybe but it depends what tax bracket the new income puts you in.

To amend your return:  If you used TurboTax Online, simply log in to your account and select “Amend a return that was filed and accepted.” If you used our CD/download product, sign back into your return and select “Amend a filed return.” You must file a separate Form 1040-X for each tax return you are amending.

Where do I enter an SSA-1099, SSA-1099-SM, or SSA-1099-R-OP1?

https://ttlc.intuit.com/turbotax-support/en-us/help-article/import-export-data-files/enter-ssa-1099-...