Hello Portaro, welcome.
Excuse me, I have not understood exactly what you mean with "add servers of gamers to my Open Arena"...
I mean, OpenArena has got its own server browser, so you should just select "multiplayer" in main menu, and should see server list (be sure to have selected "internet" servers, and check the other filters -maybe you have filtered for a specific gametype and human players only-). Does this work for you? If it doesn't work, maybe your firewall settings block OpenArena.
Also, there are other ways to find servers, I suggest using
http://dpmaster.deathmask.net/?game=openarena plus
OAwire Firefox extension (which adds useful launch links in dpmaster web pages).
(
DO NOT LINK) h t t p s : / / openarena . wikia . com/wiki/Servers#Server_browsers
(
DO NOT LINK) h t t p s : / / openarena . wikia . com/wiki/Manual/Multiplayer