Open a terminal and make sure that you are in the home-folder of your user. You can do that with a simple
Now type in this code
echo "PS1='\u@\h:\w\$ '" >>.bashrc
and press the Enter key. This will add a new prompt to your Bash's config file. Now close the terminal. The next time you open it again you will have the usual prompt.
You can tweak the prompt to your liking, have a look at this