When visiting a login page, clickable field icons will appear:
These interactive icons will assist you in filling saved logins, creating new logins, and generating passwords.
If you already have multiple saved logins for a site, you will see the field icons show the number of matching sites found. Clicking on the icon will present you with a drop down menu that will show you these matching sites:
You can scroll down if more logins are stored than shown. If you do not want to scroll to search, you can begin typing in the username and LastPass will begin to sort through and find matching results.
Clicking the desired login will then autofill the username and password selected.
Field Icons submenu
Within the field icons is a submenu that includes other available options:
Filling and Saving
See this screencast on how to save sites and log into sites