The phrase "get out there" means to go outside of the places that you usually spend all your time, which for most people is just home and work, or home and school. "Out there" is wherever people are socializing and doing active things.
You use the phrase "get out there and ___" to advise someone to be active and energetic. For example:
If you're worried about the environment, don't just talk about it. Get out there and do something about it.
To be a good salesman, you have to get out there and talk to your customers.