do u know how to design the site such that only certain membership levels can create groups?

Add a new membership actions. Then in the start of the page of create groups, Check the member ID with their allowed actions. Then you can allow them or deny them.

how do i do that exactly?

I have already discussed it here. Plz. search here.

You need to add a membership actions. you can do it by editing inc/membership_levels.inc.php

Add a line similar to
define('XXXXXXXXXXX', XX);
Then use the function CheckAction to check whether the user can perform particular action.

i'm sorry i'm very new at this... is there any way you can give me step by step instructions? because i keep trying different things and i think i'm messing up my website... thank you