You need a test rig that can hold the isolator securely, a loading mechanism of some form (often a motor and crank in the old days, now more usually a hydraulic cylinder) a way of measuring displacement, and a load cell of some sort.
I strongly suggest you visit an isoaltor manufacturer to see how it is done, the details are vitally important. An apparently satisfactory rig can give answers that are a factor of 5 in error.
MTS make suitable rigs off the shelf.
Incidentally you'll need to specify frequency range, pre loads (in all 3 or 6 directions in the worst case) and the load range for each test. Temperature may be important
