grammar - Rules for には usage

So I came across this sentence その元気な男の子にはたくさんの友達がいます。I was wondering what には was doing in this sentence. Additionally, I was wondering what the different uses and the rules for the uses of には were? So far the most comprehensive list I've found is here https://en.wikipedia.org/wiki/Japanese_particles, and the only rules I've found so far where in the Dictionary of Intermediate Japanese Grammar, defined as verb plain form or suru noun in front of には as being for the purpose of.