It appears you will need to amend your previously filed return. While you are being advised to submit Form 8453 with supporting documentation, you also indicated that your transaction information was not entirely accurate.
Before amending your return you will need to wait until such return has been accepted by the IRS. You can amend a return only after it has been filed and accepted by the IRS. E-filed returns are considered filed when you have received notice from the government that your return has been accepted. If your return has been rejected, it is not considered filed.
Mailed returns are considered filed the date you post your return.
When you are ready to amend, you can access your previously filed return, in TurboTax online, from the TurboTax home page. Scroll down the screen to the section Your tax return & documents. If you have used TurboTax CD/download, then you can amend your previously filed return by selecting Other Tax Situations, and then scroll down to Other Tax Forms.
After i filed, about 5 or 6 hours later i received an email saying congratulations your return was accepted by the IRS. So does that mean it was already accepted or only that it was received?
Accepted means your tax return is now in the government's hands and has passed the initial inspection (your verification info is correct, dependents haven't already been claimed by someone else, etc.).
So do i need to send in the forms or wait for everything to be processed?
You can send the forms needed now. But please wait until the return has been fully processed by the IRS prior to amending. Fully processed means that they either send your expected refund or issue a notice of Balance Due. Once that is completed and match your expectations based on the filed return, then amend.
Sometimes, IRS will contact you during the processing phase if they have questions, if so you can present your amended information then without actually amending the return.
IRS is not going to hold up your tax return waiting for a mailed-in detail report.
If your reported losses were true and correct, don't do anything.