How to open a file with an application from the terminal?

[redus]

I'm trying to add a line of code
source /home/...
to the end of a file. I think I need to open this file in an editor (using Atom), edit the file, save the file, and then I'll re-run the command that told me to do all of this. So how do I open a file (.bashrc, if it matters) with atom and then how do I save it so I overwrite the old file? Thanks a bunch!!

[redus]

OK I figured it out. In other words, I was told from elsewhere.
nano [file name]
edit the document
control + X
Y
Then I opened a new terminal and ran it. Not sure if you have to close the old terminal and then run the new one, but it works.

[The Cog]

If atom (never heard of it) is your favourite editor, then atom <filename> would probably have worked.

[oldrocker99]

OK I figured it out. In other words, I was told from elsewhere.
nano [file name]
edit the document
control + X
Y
Then I opened a new terminal and ran it. Not sure if you have to close the old terminal and then run the new one, but it works.

Nano has been my go-to text editor since Ubuntu 8.04, when I found that Linux is a far, far better OS than the malware magnet known as Windows.