Toward a "modern" Emacs

>> Open csv file in csv-mode
> How to do that?

M-x csv-mode (it defaults to that if you open a CSV file, though, so probably unnecessary).

>> Now, enter org-mode
> Again, how to do that?

M-x org-mode.

If you're not familiar with M-x, it is (usually) Alt-x and then you type in your command, e.g. help, apropos, whitespace-cleanup, org-mode, markdown-mode, csv-sort-fields, sort-lines, magit-blame, etc.... The set of available commands depends on your "current mode" (e.g. java, csv, org, markdown, text, mail, ...).