Can they use your computer? You can install the Desktop program on 5 computers you own. It can do unlimited returns and efile 5 federal for free. Yes it is linked to your account.
See this FAQ for why do I need to sign in to an Intuit Account this year?
https://ttlc.intuit.com/turbotax-support/en-us/help-article/license-information/install-turbotax-cd-...
