How to download and install Visual Basic for Applications
How to enable VBA in the different Office programs is described in each program subpage.
Getting started with Visual Basic for Applications
Since Visual Basic is the programming language used in all applications supporting VBA (e.g. Excel, PP, Word etc.), we have made a language introduction at Visual Basic language introduction.
There are a lot of great VBA tutorials online, so if you don't find what you're looking for in this wiki, check them out.
Some useful information when coding can also be found at Tips and tricks for coding.