Moving a blank cell in Excel on my MacBook Air

Hi,

Just an unimportant (but annoying) issue I'm having using using excel on my Mac...

When I move to a blank cell (using the navigation keys on the keyboard) and then hit 'enter', I can obviously start typing in the cell.

The problem comes though, when I want to edit a cell that already has text in it. When this happens, I use the navigation keys to move to the cell, I hit enter, and the the text in the cell is deleted! Is there a key I can hit (or a combination of keys) instead of 'enter', that will bring the cursor to the end of whatever is already in a cell so that I can add to it or edit it?

(I know I can use the mouse or trackpad to click into the cell but I am looking for a way to do this on the keyboard so that I don't have to keep returning to the mouse constantly).

Thanks!

[Re-Titled by Moderator]