supplemental applications

I was under the impression that after you submit your general OptomCAS application that schools would then send you their supplemental application if they liked your initial application. But now looking into it, SCO says you can submit their supplemental application before even submitting your application on OptomCAS and Salus wants all applicants to submit CASPer results. Am I supposed to wait to do these things until they ask me to or am I just supposed to do them? Does anyone know? Thank you!