If you haven't read
Making a definition covering open raising yet then please read it first as this tutorial assumes you have read it. A 3 bet pre flop is when a player open raises and then another player reraises. If we want to make a note on this, we just need to create a sequence with two actions. The first being an open raise by someone besides the note recipient and the second being a raise by the note recipient. Here is what the "OpenRaise" screen should look like

There are a few important things here besides what is mentioned above. The first being that we selected "action had to NOT be all-in" What this means is that the original raiser still had to have chips remaining. Otherwise it might look like an opportunity to raise when in fact there wasn't one. We can also filter on the position of the raise as well as the bet size. Finally, if we wanted to make a note for someone three betting versus hero, we can specify "player had to be the HERO" for the open raise. Next we make another raise action but this time specifying that it did have to be the note recipient

Here we can also specify bet sizes, positions, etc. For an action like a re-raise, if we're filtering by bet size, it would often be a ratio to the last bet size. For example, if we want to filter for a min 3 bet then all we need to do is set the ratio to 2 which means it's double the last total raise size. Of course you can also check if someone just clicked the "pot" button for the raise by putting the "percent of pot" as 100. If we want to rule out squeezes, which is when another player calls the open raise prior to the three bet, we need to make an action in between specifying that there was no call of the open raise. When we do that, our screen looks like this:

You can see it had to be moved between the OpenRaise and the ThreeBet
Here is the completed definition (right click->save as):
ThreeBets.xmlHere are two additional example definitions:
ThreeBetShove.xml ThreeMinBet.xml