I used the "Stash" app to invest, and now am trying to file my 1099-B. Is there a way to import it, or must I try and figure out what to put where myself?

Stash is not on the list of institutions or services that have files that can be imported into TT. 

you'll need to download the file(s).   however, you don't need to enter each transaction.  you can enter summary totals for each line on 1099-b worksheet.  then you can either 

mail your return with a print out of the downloaded file(s)

or complete form 8453 and e-file.

mail Form 8453 to the IRS  with the printout within 3 business days after

you have received acknowledgement from your

intermediate service provider and/or transmitter that the

IRS has accepted your electronically filed tax return. If

you don’t receive an acknowledgement, you must contact

your intermediate service provider and/or transmitter.

Mail Form 8453 to:

Internal Revenue Service

Attn: Shipping and Receiving, 0254

Receipt and Control Branch

Austin, TX 73344-0254

make sure box 8949 is check on the form.  

You CAN import all your tax information into TurboTax from Stash. Review the tax documents provided by Stash. The easiest way to do this is through the Stash app under Settings>Statements and Documents>Tax Documents. Copy or screenshot your account number and type of tax document (is: 1099-DIV, 1099-B, etc...) at the top of pg. 1. In TurboTax, select the financial section that corresponds to your 1099 type. After two self explanatory questions, you’ll be asked to enter your financial institute into the

search field. Type “Apex” and select Apex Clearing. Under  Apex Username type 10- and the Stash account number located at the top of your 1099  proved by Stash. The Password will be your SS#.

If unsuccessful, you’ve likely selected the incorrect entry screen.   Don’t get frustrated, I failed multiple times until realizing TurboTax has various tabs  where  importing is possible. If unsuccessful after multiple attempts, enter your 1099 “type” in the search field and TurboTax will direct you to the appropriate section.    

Replying to you post in case it helps anyone filing their taxes in 2021

You can upload it from Stash via Apex Clearing.

Go tohttps://public-apps.apexclearing.com/session/#/login  

 Sign up as a new user using your account # from your Stash tax form and type in all your info.

Then go back on TurboTax and select Apex Clearing from there.

None of the suggestions given here are working for me. Tried userid/pwd, 10-accountnumber with tax id but it just errors out.