The Tor Browser should get you online automatically after clicking the "Connect" button on the start up screen.
If it doesn't connect, there may be a simple fix. Try each of the following:
Make sure another Tor Browser is not already running. If you're not sure if Tor Browser is running, restart your computer.
'Allow' Tor in your antivirus program.
Temporarily disable your firewall.
Delete Tor Browser and install it again. If updating, do not overwrite your previous Tor Browser files.
If you still can't connect, your internet service provider might be censoring connections to Tor. Follow the instructions in the Circumvention section.
If the above steps do not address your problem, email help@rt.torproject.org with your operating system, the details of your problem, and what you've already tried.