Emacs has a nice add-on to show recently opened files. It's simple to set up and simple to use.
Add the following code to your Emacs init file (.emacs) which should reside in your home directory. ~/.emacs. Use ls -la to find it, or in Emacs use Ctrl-x Ctrl-f ~/.emacs.
; Recently Opened Files - use recentf
; Enable recentf mode
; Show last 10 files
(setq recentf-max-menu-items 10)
; Reset C-x C-r to display recently opened files
(global-set-key "\C-x\ \C-r" 'recentf-open-files)
As you probably know, in Emacs init file, any line starting with a semi-colon (;) is a comment and ignored by Emacs.
Save the init file and restart Emacs.
Hit Ctrl-x Ctrl-r to get a list of recently opened files.
Scroll to the file you want open and hit enter.