First hack is pretty easy, and I appreciate MxRugg taking the time to post up some help. I found my first attempts at hacking, especially in regards to stops and nukes, very confusing. So to help with this, I too put together a little tutorial. You can find it under the 50-hacks achievement.
But before you follow that link, I'll leave you with one tip: Save before you hack. Always! Thus, if you fail, just reload and start again. This is crucial in the beginning, as hacking does take some practice, and hacking becomes very important later in the game, especially for a stealthy playthrough.
Good luck!
PS. My "thumbs up" to MxRugg got taken away since I've entered my own solution.