When you create a new report, only you (and administrators) can see it. You can share your report using the "Share" button when you are editing your report.
You can choose to share your report with some specific users and/or with a group of users (profiles), and define if these users will be availabe to modify it or only view it.
1) Manage this option by configuring the profiles.
You can for example create un standard profile dedicated for your agencies and lock the possibility of accessing all of your data
2) Manage this option by configuring user rights
Your can now share a report with this new profil.
When the option "edit Dataset" is off the user will not be able to edit the data set in the report
Dont forget to publish the report ! otherwise the partner will not be able to display the report.