Your male friend finds it hard to meet girls, and has asked for your advice on how to find a girlfriend. You think your friend is just too shy and needs to be more outgoing. You say:
You just need to get out there and talk to people more.
Telling someone that they "need to" do something is a very direct way of giving advice or orders. Because it is so direct, you should probably only use it to give someone advice if they have asked for your advice. Otherwise, it can come across as rude.
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.
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