着替える (kigaeru) means “change clothes, get changed”

More examples

学校へ行く前に着替えます。gak kō e i ku mae ni ki ga e ma su

I get changed before going to school.

汗をかいたので、帰宅してすぐ着替えました。ase o ka i ta no de ki taku shi te su gu ki ga e ma shi ta

I changed clothes as soon as I got home because I was sweaty.

Refers to replacing the clothes one is wearing with another set, often when the time of day or activity changes.

身に着けている衣服を別のものに替える。mi ni tsu ke te i ru i fuku o betsu no mo no ni ka e ru

着る (kiru, "wear") combines with 替える (kaeru, "replace") to form 着替える (kigaeru, "change clothes").

着替える (kigaeru) commonly appears in everyday phrases about changing before bed, after exercise, or for a special occasion.