You should probably install a regular version of Firefox and use the Tor Browser for when you want to use Tor.
This has various benefits. The Tor Browser Bundle includes a version of Firefox that is a fork, which means it has a modified source code in order to increase your privacy/anonymity.
The Tor Browser is run highly separated. You can run the Tor Browser and a regular Firefox instance at the same time. The configuration is completely separate. This prevents you from leaking information that would allow an attacker to determine who you are, even when using Firefox with Tor.
Since you also shouldn't use any other plugins (Flash, Java, ...) or Firefox Add-ons in order to not accidentally leak information on who you are it is way safer to use both the Tor Browser and Firefox as separate instances.