Is Sublime Text free to use?

Sublime Text is distributed as shareware. It can be downloaded and evaluated for free without any enforced time limit, but a license must be purchased for continued professional use.

How do I install plugins in Sublime Text?

You can install plugins by first setting up Package Control via the Command Palette (Ctrl+Shift+P or Cmd+Shift+P), selecting 'Install Package Control', and then using 'Package Control: Install Package' to search for and add extensions.