Sorry Andy, but you’ll really need a modicum of unix command line knowledge to get much further.
Of course the system allows creation of files beginning with dot; if you open textedit, you move to “make plain text” and try to save a file whose name begins with a dot, it will tell you, as you state, that files beginning with a dot are reserved for the system. AND THEN IT GIVES YOU THE OPTION of doing it anyway, or cancel. You just need to click on “do it anyway”, which I think is called “use .”.
But instead let’s make this quick and be done with it. Copy and paste the following lines VERBATIM onto your console. They will create the .bash_profile file, put the relevant lines inside, and then source it to incorporate the environmental variables into your current running shell.
cat >> .bash_profile <<eof
You can verify that it created a good file by editing it
should now open it onto textedit.