This is the 504th most frequent Japanese word.
使い
"Use" or "usage."
Here, '使い' refers to 'usage' or 'the way of using' as a noun when paired with '方' (kata).
この道具の使い方を教えてください。
Please teach me how to use this tool.
In this sentence, '使い' means 'use' or 'usage' as a noun, describing the action of utilizing something.
彼女はほとんどの時間をゲームの使いに費やしている。
She spends most of her time in the use of games.
Here, '使い' is implied as 'usage' indicating the complexity of correctly using a particular term.