Clan Wars (CW) is https://www.warzone.com/Clans/War
Every clan on WZ has a CW rating, which you can find on each clanpage.
A player can play as many games as he wants, but at most 1 per day (UCT timezone).
To get ranked as a clan in a CW season you will need to conquer territories, the more territories a clan conquers the higher their ranking. You need 3 wins for the first territory, and the number of wins per territory slowly increases after that to a cap of 20 wins/terr (iirc).
The territories dont really matter, cause the final ranking is based on the number of games won in a season (which just happens to match up with territories taken).
If you want to play in CW you will need to join a clan and join a timeslot. The slots open every 4 hours, and a countdown to the next slot can be found on the CW page. Once you joined a timeslot you can pick from 3-5 templates.
CW games are made on the first 7 QuickMatch templates, the French Brawl QM template and the Guiroma QM template.
Please note that if you want to play the 2v2 template, you will need to join the 2v2 template with a clanmate in the same slot.
Games are created starting with the clans with the highest rating (not ranking), and then working down the rating list. This might cause clans with a low rating to get free wins.