Let's get started:

1. Open up vSphere Web Client and log in to the vCenter Server.
2. In the Storage section, select Datastores.
3. Choose the datastore from the list of datastores in the left panel where you want to prioritize the I/O:

4. Click on the Configure tab, then click on the Edit button in the General section.

5. At this stage, you can enable SIOC by simply selecting the checkbox labeled Enable Storage I/O Control. Click on the OK button when you're done:

6. You'll know you were successful if, in the vSphere Web Client window, you now see Enabled under the Storage I/O Control item of the Datastore Details section:

7. Do the same thing on your other shared storage datastores.