1. Go into phpMyAdmin in your web browser and enter your login and password : you should see a screen like this :

2. Now, find your database on the left part of the screen :

3. You should see something like this :
Top of the screen :

4. Look for the SQL tab and click it. Once you are on this page, copy/paste the SQL query to run into the box :

5. Click on "Go" (or Execute) :

6. Now, you should see a page like this :

7. If you get a message error, like this :

Just read the error message and correct the sql query and try it again.
If all has gone well you have then successfully executed a SQL query using phpMyAdmin.