According to the first law of thermodynamics, overall energy will be conserved

According to the first law of thermodynamics, overall energy will be conserved. Therefore, if you end up putting a lot of energy into a chemical reaction (i.e. it is highly endothermic), that means the energy most likely must be stored in there with the potential to be released at a later date (in other words, endothermic reactions raise chemical potential).

Likewise, if we have a chemical reaction that releases a lot of energy (exothermic), that energy had to come from somewhere...that somewhere being stored up chemical potential (much like a boulder rolling down a hill releases gravitational potential). I hope you understand!!!