You can install the stable version of DesModder directly from the Chrome Web Store. DesModder is currently only supported for Google Chrome and Chromium-based browsers such as Opera, Brave, and Vivaldi.
The extension updates every few weeks (see DesModder releases page for a history).
If you want to get new features early, follow the instructions in https://github.com/DesModder/DesModder/wiki/Development#Setup, keeping in mind these may not always work at all times.