In your Pharo image, open the Playground (Ctrl+OW) and execute the following Metacello script (select it and press Do-it button or Ctrl+D):
Metacello new
onConflictUseLoaded;
baseline: 'CormasOpenMole';
repository: 'github://cormas/cormas-openmole:main';
load.
To check if installation is correct, go to the Cormas-OpenMole-Tests
package and run all the tests.