To create and run an MDX Script in Analysis Services, you need to be in SQL Server Data Tools (SSDT) with a cube already created and ready for editing.
To create a Multidimensional Expressions (MDX) script
Open the cube for which you want to create an MDX script, and under View, click Calculations.
If you are not in Script View mode, click the Script View icon.
In the script window, under the CALCULATE command, type an MDX expression. Click the Check Syntax icon and verify that the expression is syntactically correct.
To run the MDX script, deploy and process the cube with the new MDX script changes.