COAKES

So I am beyond novice with regards to RCs but need a little help please. Been using the stock 2000 nimh battery and got a further 3000 nimh one. Both have been pretty useless from the start and only last a few minutes each. I’m guessing we fried them??? Just got a 5000lipo 2s 7.4v battery and charger. Charged battery and put it in last night. Moved the little connector to the Lipo position, Steering works but no power. The motor is trying to move but then stops immediately and it is making a beeping noise. No idea what’s wrong. Would love your friendly help with this please. Keep it simple though! Thanks in advance.