Help Beginner Roth IRA: no clue where to start

I’m 24 and opened & fully funded my Roth IRA back in January, but I never actually invested the money (It’s been sitting in cash this whole time -- I know that’s not ideal).

I'm investing for the long term and thinking of something simple like a total market index fund. Any tips on what to do next (or what not to do)? I see VTI a lot on this page, is that good?

I clearly have no idea what I'm doing and would appreciate any advice!