Just do what it says when you're installing it.
But, since I have some free time, I'll give you a tip.
Whatever folder you installed OP2 to, install Renegades to that folder + "modren" (so, for example, if you installed OP2 to "C:\Sierra\Outpost 2 Divided Destiny\" you'd want Renegades installed to "C:\Sierra\Outpost 2 Divided Destiny\modren\"). I'm pretty sure it automatically does that for you, though, so just give it your OP2 directory. Then, run the Renegades shortcut.