You load it like a cartridge. If you look close at the picture you will see that the body is split. After you chamber the tool you open the action, the extractor will grab the rim. As you open the action the tool expands to grab the cartridge neck thus extracting the case.
The tool comes apart so you can remove the case from the tool.
If this is bolt gun you can use a .45 caliber cleaning brush on a cleaning rod. Just push the brush into the case. When you pull the rod back the brush grabs the case. Case should come right out.
.308- because people have a strange tendency to get behind things when you start shooting at them.