adding link to the prerequisites

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cc: @batamig

Author: Shereen-Bhar

articles/defender-for-iot/organizations/tutorial-onboarding.md

@@ -41,6 +41,8 @@ Before you start, make sure that you have the following:
     | **Maximum bandwidth** | 2.5 Gb/sec | 800 Mb/sec | 160 Mb/sec |
     | **Maximum protected devices** | 12,000 | 10,000 | 800 |
 
+- An understanding of [OT monitoring with virtual appliances](ot-virtual-appliances.md)
+
 - Details for the following network parameters to use for your sensor appliance:
 
     - A management network IP address