You read and search for your needs. Depends on your OS. Since XP my AV has been Avast! but recently nearly changed it after an upgrade. It's OK now and use 7's own firewall. I bought SAS pro for antimalware but you could buy MBAM instead. I also use the free Spywareblaster and need to update manually. I usually forget but kind posters here will remind us. Running like this for years with no ill effect and also using common sense browsing. McAfee free site Advisor is another good addition. No suite is perfect but you have Norton, McAfee,BullGuard, Kaspersky and many more you can pay an annual fee. If you get infected by running these suits I don't think they'll reimburse you if you do get hacked. Poor protection if you think about it..
What is ransomware and how do I protect my PC from WannaCry?