Of course, ATM comes with its own instructions. It’s important to note, however, that all pre-GX versions of ATM have two parts: a control panel and a driver file. The control panel goes into your Control Panels folder (System 7) or loose in the System Folder (System 6). (Ever wonder why the control panel is called ~ATM? It’s to force ATM to load last, after all your other control panels and extensions have loaded at startup.)
The driver, however, has to go loose in the System Folder, whether on System 6 or System 7.
Your ATM disks actually come with two versions of the driver. The one called 68000 is for the Classic, PowerBook 100, Plus, and SE series Macs. The one called 68020/30 is for all other Macs. You can have them both installed with no ill effects, but you must have at least the one that’s right for your Mac.