First, check out Is it Safe to Upgrade? if you have any concerns or questions. Once you decide to "make the switch," follow these suggestions:

1. Back up your database
2. Copy any custom CSS, functions, sections, etc into a text editor
3. Move all of your widgets to the "inactive" area (Appearance -> Widgets)
4. Follow these instructions on how to install & activate PageLines
5. Reestablish your Wordpress menus (Appearance -> Menus) and save
6. Move all of your widgets back to the desired locations (Appearance -> Widgets)
7. Visit each tab of the PageLines menu and adjust the settings to your liking (don't forget to enter your account info too!)
8. Paste your custom CSS, functions, etc that you copied earlier back into your site.
   There are three ways to do this:
   • PageLines Customize Plugin
   • Base Theme
   • Custom Code Settings