AffiliateWP has a separate shortcode for the affiliate login form . This shortcode allows you to place a login form on any page.
Usage:
[affiliate_login]Redirect
If you’d like to redirect your affiliates after they login to a page other than the Affiliate Area, use the redirect parameter of the shortcode:
[affiliate_login redirect="http://yoursite.com/new-page"]Note: You will only see this form if you are logged out. No WordPress login form will display if you are already logged in.