Where

Step 1: Get to level 30.

Step 2: Do your placement matches and get placed in bronze/silver/gold 5

Step 3: Look on boards to find a team suitable to your solo Q rank

Step 4: Look on boards to find tournaments by searching for ''tournaments'' and restricting your search to 1 week or 24 hours.

Step 5: Profit

PS: You can skip step 3 sometimes because some tournaments are 1v1s or free agent tournaments in which you are assigned a random team.