What Citrix login are you referring to? Remote desktop access (or access a Windows desktop app, without the desktop part) from within a web portal/browser via Citrix web portal?
If so, you're not likely able to do much in this area. That Citrix interface is hybrid web + custom stuff that exposes a remote desktop. Selenium2Library alone only handles the Citrix portal part, it can't do anything to the remote app/desktop. AutoItLibrary and similar tools won't work there since they're not likely installed on the remote desktop.
Your best alternative might be to hack automation support for this using image recognition of the remote app/desktop within browser via use of Sikuli(Library), etc.