Page for Portfolio (Same goes with "Posts page")

I am creating a plugin “Portfolio”.

In the plugin configuration screen, I created a <select name=”page_for_portfolio”> (the idea is to equal the “Front page / Posts page”).

How do I show the Portfolio (projects loop)? Not the Portfolio ‘page’.
(Same goes with “Posts page”).

** My question is not the loop.**

Thanks

[Sorry my bad english]