Connect them as shown and measure a reference value for your launch cable output, just like you would to measure the loss of ST cables. Test your reference cables for loss to make sure everything is top quality. Now, attach the ST connectors on the reference cables to hybrid splice bushings and attach the cable to be tested to the launch cables. The meter will now read the correct loss for the cable. Here we need a adapter for the meter matching the connector we wish to test and at least one cable with ST or other connector matching the output of the test source and the connector style we wish to test on the other end.
Lets use Biconic connectors as an example with a SC source.
Place the Biconic adapter on the meter, and attach the Biconic to SC cable on the source and measure the output for a loss reference. Then attach the launch and receive cables to the cable to test and measure the loss. Substitute your connectors in the drawings above for your specific test. Getting the Right Components Fotec and most distributors sell hybrid adapters and patchcords for testing. They may not stock all varieties but most can be ordered for delivery in a few days.