"Go Play In Space" is a very good place to start. It will give you the basics of spaceflight that you will need in order to get to another planet.
Once you get the basics (Launch, adjusting your orbit, etc) you sort of have three choices.
1; You can use the "stock" MFD's, such as TransferMFD. This is the hardest path, and isn't very fuel efficient. You will likely have better luck with choices 2 or 3.
2; You can use TransX. There is an older version of TransX included with Orbiter, but you'll need to activate it in the "Modules" tab on the Orbiter Launchpad before you can use it. There is a newer and better version available.
[ame="http://www.orbithangar.com/searchid.php?ID=3039"]TransX[/ame]
As far as I know, this version works in Orbiter 2010.
Several excellent tutorials for TransX can be found here:
http://www.flytandem.com/orbiter/index.htm
3; You can use IMFD (Interplanetary MFD). IMFD is probably the easiest tool for beginners, and includes an autopilot to orient the ship and make the burns:
http://koti.mbnet.fi/jarmonik/Orbiter.html
A comprehensive tutorial for IMFD can be found here: [ame="http://www.orbithangar.com/searchid.php?ID=4142"]IMFD Full Manual/Playbacks[/ame]
Whatever method you use, you WILL need to have a basic understanding of orbital mechanics, and how transfers are made. This is, after all, Rocket Science!