How to add NBT data to an entity on spawn

 Hello, I have been trying to get custom entities to partake in raids. I have managed to get them spawning in the correct place, but they don't go towards the village center. Nor do they receive any of the buffs that raiders get, like speed. I went searching in pillager data and I found the tag "CanJoinRaid". I looked it up on google and appaently it allows the mob to join an active raid. If I could give this tag to my mob, I think it would instantly join it to the raid. I just don't know how to give entities NBT metadata tags. I wouldn't mind editing Mcreator files, if it was necessary. Any ideas or solutions?