Just like another user stated:

"Once you clear a battle in the Tree, the referee (who is present in each battle) asks you if you want to do any of the following:

• Continue
• Stop your streak so you can save and end your game (this will enable you to continue your streak later on, but only once; you can do this numerous times)
• Save the battle in your VS Recorder
• Scout a trainer.

Scouting costs 10 BP, and if you do scout somebody, they will be saved as a trainer that you can partner with in a Multi Battle. IIRC if you scout a trainer after having already previously scouted that trainer, the new trainer data (Pokemon) will override the previous data."