Before you can make a start, you need to add the Developer ribbon to the top of Excel.
If you have Excel 2007, click the round Office button, then click Excel Options at the bottom. When you get the Options dialogue box up, click on Popular from the left in 2007. In the section labelled "Top options for working with Excel" check the box for "Show Developer tab in the Ribbon":
In Excel 2010 and 2013 click the File menu then select Options. From the dialogue box, click on Customize Ribbon on the left side. From the right hand side you'll then see an area called "Customize the Ribbon". Under "Main Tabs" check the box for Developer:
When you have the developer toolbar, you'll see the following tab in the Ribbon (this is from Excel 2013, so you may not have all the items below):
In order to run macros without any annoying security warnings, click on Macro Security, on the Code panel. Select the option for Enable all macros. Then make sure that "Trust access to the VBA object model" is checked:
NOTE: If you're worried about macro security then you can always bring this box up again and disable the macros before you exit Excel.
Now that you have the developer tab added to the Ribbon you can do things like bring up the Visual Basic Editor, run macros, record macros, and insert form objects onto your spreadsheets. First, let's have a look at the Visual Basic Development Environment. This is, after all, where you'll be writing all your code.