How do I switch between accounts on MT5?

To switch to another account on MT5, double-click on it in the Navigator. Demo accounts are marked by the green icon, and live accounts with the golden icon. 

Go to Navigator, choose the account you want to switch to on the list and double-click on it. A window with credentials will pop up, and you just have to click okay. 

If you don't see the account you want to switch to, just right-click on any account --> Login to the trading account --> enter the credentials for the account you want to log into and you are good to go!