Where do you upload a copy of my 1099B for Turbo Tax to send to IRS? Turbo Tax prompted me to upload it. I selected "upload it later" Now prompt is not there.

Please follow the instructions below to import your 1099-B (if you do not want to enter it manually):

1. Login to your TurboTax Account 
2. Click on the Search box on the top and type “1099-B”
3. Answer "Yes" to  "Did you sell stocks, mutual funds, bonds, or other investments in 2019?"
4. Answer "Yes" to "Did or will you receive a 1099-B form or brokerage statement for these sales?"
5. Enter your bank's information to import the 1099-B

The previous answer from @DanaB27  doesn't address this question at all, but is instead about getting the 1099-B data into TTax for tax preparation.

TurboTax only allows upload of one file with this e-File process, so the challenge here is that's the file you designate to upload with the signed Form 8453-FE.  If that is a PDF file, you can use a commercial PDF editing program to insert or append the 1099-B pages to it, but you must do this before you designate it for upload.  There isn't a way to upload a second file or any file after you've submitted the e-Filing, and the TTax software doesn't tell you about this when you're doing your e-Filing, even though you may have checked the box(es) to enter summary amounts for 1099-B data.