Hi @dstokes!
This post from my colleague Darren might help you out: How can I define an Atmospheric Boundary Layer in SimScale
Here is a doc entry for CSV tables which partially helps to understand tables in different scenarios: Tables | Boundary Conditions | Documentation | SimScale
Regarding time steps, my colleague @rszoeke has posted some useful information here: How can time step and write options be made more intuitive? - #3 by rszoeke
The first link I provided should answer your question, please let me know if you have any doubts or other questions - happy to help you out!
Jousef