On the Olympus/OM System OM-5 you can set it to manual focus (MF).
The simplest way:
- Press OK to bring up the Super Control Panel.
- Find the AF mode setting — it may currently say S-AF, C-AF, etc.
- Select MF.
- Turn the focus ring on the lens to focus manually.
You can also make manual focusing much easier by enabling Focus Peaking, which highlights the edges of objects that are in focus, and Magnify, which enlarges part of the image in the viewfinder/screen.