To expand upon post #2 a little bit: there are a few ways to simply "create a file":
shell$ touch ~/.bashrc
shell$ echo > ~/.bashrc # warning: this will ERASE a pre-existing file and make an empty one!
if you're in a terminal, you could use a text editor like nano:
shell$ nano ~/.bashrc
That opens up the file in the nano editor. You can put commands in there, and save the file by pressing CTRL-o, ENTER, and exit nano by pressing CTRL-x.