Well you can do 1 of two things:
1. Use a dongle to JB your console every time you boot it. You can get the last Hermes payload here: http://www.ps4news.com/forums/ps3-ha...ip-114958.html
2. Install the Hermes 3.41 CFW. See this thread: http://www.ps4news.com/forums/ps3-ha...es-117272.html
I recommend the CFW method, as it is a lot more convenient. You can also consider upgrading to a 3.55 based CFW like Kmeaw if you so choose, although that kinda defeats the point of the downgrade. I personally use the Hermes CFW v3.41 w/ his v4c payload right in the XMB.