KeeFox is available as a Firefox add-on from the official Firefox add-ons website. Please read the add-on description and then install it as you would any other add-on.
During development of new features there will be times when it is useful for a snapshot of the addon to be tested by a small number of volunteers. This version could contain significant bugs but will also be the first to receive new features and bug fixes. It is not guaranteed that this version will always be newer than the beta version or stable version since some new features or bug fixes will skip this version and go straight to beta testing. Also note that you will not be automatically updated to new versions of this experimental version so be careful to not get left behind!
The newest experimental version is here: https://github.com/luckyrat/KeeFox/blob/master/XPI-package/latest.xpi?raw=true
The latest source code is available on github: https://github.com/luckyrat/KeeFox