You cannot change or add anything on the return that you just e-filed, nor can you stop it. It is too late, just like when you put an envelope in a US mailbox on the corner. The IRS does not allow you to take it back.
If you left out a W-2, a 1099G, or a dependent, or a 1099 etc…DO NOT change your return while it is “pending.” The changes will go nowhere.
Now you have to wait until the IRS either rejects or accepts your return. If your return is rejected, you will be able to go into your account and make the necessary changes to your tax return and re-submit your return.
If the IRS accepts your return, however, then you have to wait longer until it has been fully processed and you have received your refund. THEN you can prepare an amended tax return and e-file or mail it in. You have to be able to work from that return exactly the way it was when it was e-filed originally. You will need to use a form called a 1040X.
Meanwhile, DO NOT go in and start changing anything on your return in the system, or you will make a mess for yourself. Sit tight and wait until you see what the IRS does with the return you just e-filed
The Form 1040X you need will not be available until late February.
The only way to add something after you’ve filed — and the IRS has accepted your return — is to file an amended return.
If the IRS rejects your return, you can make changes before re-filing.
You may not have to add Form 1099-S if you reported the property sale. If you sold the property and did not report it, then you probably will have to file an amended return to show a gain or loss.
The 1099-S issuer sends a copy to IRS and they will be trying to match the form with a property sale on your return.
Wait until you receive your refund before doing anything in case the IRS corrects your return.
See How to Correct Federal Tax Returns and How do I amend my federal tax return for this year?