Most exams have online registration available and those that require paper applications can be found on the SOA/CAS websites. You can learn about exam registration through the SOA’s exam site or through the CAS’s exam site.
More information regarding deadlines, instructions, refund policies, etc. for the Exams P/1, FM/2, MFE/3F, C/4 is also available at the Be An Actuary’s website.