Hi umm as you can tell from the title i am new to this program and wondered if any1 could help me, My overall goal is to make a tower defence game that i have planned, But i have no idea where to start, i also only have the free version if that helps or makes it more complicated 
please could somebody tell me where to start, Thankyou:)
Start by learning the basics of programming.
Welcome.
might be an idea to hit the Resources link on the Unity website, Go through the tutorial resource samples they are really quite useful.
And check out what is available on the Unity Asset Store Cntrl+9 within Unity will bring it up.
A new asset in the store should be available soon Tower-Defense useful for Pathfinding on Grid
and use the search function in the forums
JRavey is right learn UnityScript or #C Unity Documentation
Have further Questions feel free to ask in the forums
Or just dive in, get overwhelmed, then give up. Really, you’re going to need to learn some programming or link up with somebody who can program.
www.unitystudent.com , easy to follow tutorials. Also check out some tutorials about unity-interface at:
http://unity3d.com/support/documentation/video/
and a few tutorials here:
http://unity3d.com/support/resources/tutorials/