To Pile Something Up
To Stack Up, To Load
transitive verb, godan verb
You learned that 積もる (to accumulate) is used when something like snow or dust piles up over time. 積む is the transitive version, so it means to pile something up, to stack up, or to load. You know this because you are the one moving (む) things to pile them up!
積む is often used for physical actions like stacking boxes or loading luggage, but it's also used in more abstract ways, such as building up experience or skills. Think of it like "stacking up" experience points to level up in your life!
The reading comes from 積もる, so pile up your knowledge and remember it that way.
荷物を積むのに少し時間がかかるから、そこで待ってて！
It will take a little time to load the luggage, so wait there!
アイツは地道にコツコツ経験を積んで、今の地位を手に入れたんだよ。
He steadily and diligently accumulated experience and earned his current position.
それじゃあ2人組を作って、トラックに七面鳥を積み始めて下さい。
Now please grab a partner and begin loading the truck with turkey.
彼の積ん読リストには、たくさんの本が積まれていた。
His "to-be-read" list had many books piled up.