This is the 7731st most frequent Japanese word.
取り付ける
"To install" or "to attach."
Here, "取り付ける" is used to describe the physical installation of an item, in this case, an air conditioner.
彼は新しいエアコンを取り付けました。
He installed a new air conditioner.
In this sentence, "取り付ける" refers to the installation of an intangible item, the software, onto a tangible device, the computer.
このソフトウェアをコンピュータに取り付ける必要があります。
We need to install this software on the computer.
It exemplifies the word "取り付ける" referring to affixing an item, a mirror in this case, to a wall within the room.