There's a lot of different ways to accomplish what you want here. The question is a bit confusing because you are talking about Excel, but then you table about '/var/lib/postgres/myfile1.csv', which makes me think you are now using some favor of Linux.
I'm using Ubuntu 12.04 with pgAdminIII 1.16.0. And I have Open Office installed with LibreOffice 3.5.4.2 as the Excel replacement.
I'm not sure why you want to take the information out of the grid in pgAdminIII, but assuming just wanting to take the data and move it over to a spreadsheet to play it for some reason, then about the easiest way to do it is run your query and click the upper left corner of the results (which just like a spreadsheet selects everything) and copy. Then, you should be able to open LibreOffice and paste in the information. It will bring up the same dialog as you would see when importing a CSV file.
Also, you should be able to start psql and then do a "COPY" command. If you get a permissions error, then try the suggested "\COPY" instead. Please see the PostgreSQL docs. Here is a link to a wiki page here.
If I'm missing what you are trying to do, please ask questions in the comments section, and I'll try to improve my answer accordingly.