Several times people ask question “How to give administrative rights on analysis server”? So let’s discuss on this topic. The users belong to server administrators have complete access to the features and functionality of the SSAS instance like complete access to all SSAS databases on that instance. If you want to assign administrative rights to any user then follow following steps for doing the same.
Connect to the analysis services instance by user with administrative rights, right click on instance name and select "Properties" option; it opens “Analysis Services Properties” window.
In “Analysis Services Properties” window, click on “Security” tab.
Now click on “Add” button, it opens “Select Users or Groups” window.Enter the active directory user to whom you want to give server administrative rights and click OK button.
Now Active directory user will appear under the list of “Server Administrators”. Click on OK button.
For BOL article,you can refer;