I forgot to add another w2

if you submitted it the return at this point can't be recalled. the IRS won't open e-filing until 2/12/2021. so you'll have to wait. if your return is rejected you can fix it and resubmit. if it is accepted you'll have to wait until it is fully processed and then file an amended return. it is possible the IRS will make changes to your return and adjust your refund accordingly so you won't have to amend. watch for a notice from the IRS telling you what to do. 

If you have already e-filed your return, it is to late to add another W-2. You would now need to wait until it's either been accepted or rejected. If it's rejected, you can simply go in and fix the error, add the W-2 and re-submit your return. If it's accepted, you would want to wait until you receive your refund and then use the link provided below to amend your return:

How do I amend my 2020 TurboTax return