Open sublimetext site in your browser https://www.sublimetext.com
Then click on “Download for Ubuntu” link , a .deb file which name similar to “sublime-text_build-3126_amd64.deb” start download on your system.
after download finished do right click on that downloaded file and open this file with option “open with software install”. Ubuntu software center will open then click on install button. After that installation will start and you can run Sublime after this process will done.
Please note : Sublime Text may be downloaded and evaluated for free, however a license must be purchased for continued use. There is no enforced time limit for the evaluation.