How and what to buy for Fidelity IRAs

I recently rolled some money over to fidelity from betterment. Betterment did all the work for me but I figured the lower fees would be better. I’m clueless and would like to set it and forget it. What funds should I plop my money in?

Also, how do I do it? I have around $40k in there but only about $500 available for trade. Do I sell my other positions, wait for that to settle, and then buy what I want? Or is there a way to just swap? I want to make sure I don’t trigger any tax consequences!