Only need to enable this if you are on a lan . And IF you are , not really necessary . Will it add some security ? Maybe . Again . I doubt it would be necessary for you to enable it . You can if you wish and see . But it is protection for a lan environment
If you didn't receive constant ip confilct warning or losing your connection with no reason, you don't have to. In fact, no personal firewall can completely solve this attack. You may consult your lan administrator or read some books about ARP protocal.