Was pretty much all I need to get started (I'm using one of their third party wrapping for .NET)
I guess it might get slightly more complicated if you are doing recurring billing or customers but their standard template should be sufficient for your needs at this stage. I pretty much took this example:
2) Pulled their API wrapper (they have PHP library) - I think the only part that needs updating is your API key
3) Followed their example listed on the page
and everything worked. Let me know if I can help further!
Does that make sense?