Need to add fb login button into my sidebar login

I've got a sidebar login on my homepage
I don't want to use standard wp login page (don't want my users to move from page to page).Therefore I need to add login button and place it under sidebar's login button. I can't use shortcodes for that (I could place them in widget area but it looks bad.
Would you be able to give me a part of code or a link that i should paste so it would lead to display login button from the plugin, like it does in wp login page?
Can you help somehow?