How do I select and change a text? I know this is a stupid question, but for some reason I can't select a text to change it. I've tried right clicking and hitting Tab but for some reason it is not letting me change what the text says. Please help. 

The following should be noted:
I'm using a MacBook air,
I am using Bender 2.71, 
And I am very new to Bender.
If the Tab key for some reason doesn't put you in Edit Mode, try changing into edit mode using the dropdown menu:



You can find more information about text editing in the manual: http://www.blender.org/manual/modeling/texts/introduction.html#editing-text

Also, if you are a new user and do not have special reasons, there is no point in using an older version. Try the latest release, it's faster and has more features.