S90 that's a very old version, but I would go to https://darksoftware.xyz/PS4/FWlist (I trust it) and get 9.00, which is the generally best version, as every jailbreak type recently done works on it, including webkit exploits, ppw,n, and the BD-JB lapse iso exploit
After you go to the website, download whatever version you feel fits you best, make a folder on a drive, PS4, then make a folder called UPDATE, and put the PS4UPDATE.pup inside that folder (the file you downloaded from the link), and update through safe mode all of the recent exploits can be done offline (ppwn and BD-JB only) so dont worry about wifi setup unless you just want to do the webkit exploit.
