You can connect your BGG account, this way you will search only the games you own.

To get your sessionId, you need to look at your cookies for boardgamegeek.com via the developer tools of your browser. Here's how to do that:

1. Go to boardgamegeek.com
2. Open the developer tools of your browser (click here to see how).
3. Go to storage (depending on your browser, it could be in the Application tab).
4. Look for the cookie named SessionID; the value should be a string of 40 random characters, then a 'u', and then a number. It should look something like this: 1154a14d4d586b2c5f155e18dd2b2x9e2044e51eu19839
5. Copy this value (of the cookie) and paste it in the
   "BGG SessionID" field in this tool, and you're good to go.

ATTENTION: This value of the SessionID changes every hour, so you might have to do it more than once.