How do I upload my 1099-B?

If by "upload" you mean attaching a 1099-B to your return, Turbotax does not support those types of attachments.

TurboTax will figure out if you need to provide the IRS with a copy of your 1099-B.    If you do need to include this form, you’ll be prompted to upload a PDF copy after you enter your sales section totals in the investments section of TurboTax Online (TurboTax Desktop doesn’t support 1099-B upload).   You can download or request a PDF copy of your 1099-B from your broker’s online account.

Where do I enter or import a 1099-B?

From:  When do I need to include my 1099-B with my return?