yes, you can add a link to your pages that will point to the Login Page created by security assist.
to display the users name, you will need to edit the Security Assist Authenticate User behavior on the login page. Go to Window -> Server behaviors to open the server behaviors panel, in the list of server behaviors, double click the Security Assist Authenticate User behavior to edit it (you may have 2 instances of the Security Assist Authenticate User behavior on the page, you will need to edit both if you do).
On the first step, you may or may not want to change the success redirect to point to another page.
on the third step of the Security Assist Authenticate User behavior, you can select columns from the user table to store in session variables when the user logs in, click the plus button and select the Name column to store the users name.
on the bindings panel, expand the session section to access the binding for the name session variable, you can add that binding to your page to show the logged in users name.