Well i just got my macbook yesterday and i am familiar with garageband, all i need now is to know how to plug my guitar into my MacBook. What do i need to do and also what do i need to buy to plug it in? I don't want to spend over £70.

Make sure you guitar is electric or electro-acoustic. You need a lead(cable) to connect guitar to your mac book. they basically ship with 3.3mm jack. You should connect one end to the guitar. Now for the next end you need to buy a adapter.
(1/4” to 1/8” Adapter - Record an Electric Guitar on Mac)

http://cgi.ebay.co.uk/1-4-to-1-8-Adapter-Record-an-Electric-Guitar-on-Mac_W0QQitemZ280221577486QQcmdZViewItem

Now you should be fancy enough to connect your guitar to mac line in port and get your Mac busted LoL

Rock on!!!!!!!!!

to plug ur guitar into ur macbook get an audio in cord and an extension to make one side fatter plau the smaller part into ur macbook mic hole and the fatter part into ur guitar