Ranked battles are rare events that come up around one weekend every month or two. So far they have been between tiers 5-10. Make sure you keep a lot of different tiers in your garage for the next time ranked battles are available again or you will be spending some silver.
To get to ranked battles you must go past the title screen, server select, and initial loading screens. Where you have the chance select 'multiplayer', 'ranked battles' will be right beneath it.
Once you begin,
STAY IN THE MATCH UNTIL THE END! Even if your vehicle is destroyed, wait until the result screens. If you skip to garage it may not count.
The only way to know if ranked battles are coming is to do some reading. These are the following places to find the information.
1. Read the game log in the garage by using RB/LB buttons.
2.
WoT Console Official Site3.
WoT Console Forums4.
WoT Console Facebook page5.
WoT Console Twitter page6.
WoT Console Reddit Subreddit page