If it's not complicated, how come you can't do it?
Seriously, as pirateghost said, based on what you've said so far, don't virtualize FreeNAS. It's not recommended for a number of reasons. Search the forum to find out why.
If I had to guess, less that 5% of our user base, could install/run FreeNAS on ESXi correctly. Others have tried, skipped corners, and lost their data.