I created a model using the fit command and an algorithm (like: | fit PCA k=3 into "my_PC_model"). I did it in an application that is not the Machine Learning Tool Kit and I want to share my model with other users. When I list the models (command: | listmodels) I see that the model is private and I don't know how to change the sharing.
You need to change the permissions on the model file so another user can use it . If you want to send that model to another instance of splunk you have to place the model file (lookup) in the MLTK in that new instance and set permissions.
Check the MLTK FAQ as well.