This post will explain how you can enable TLS 1.1 and TLS 1.2 in fiddler so you can test your Web Apis with TLS 1.1 or 1.2. In order to do this, navigate to
Tools --> Options --> HTTPS
You will see the below screen
If Decrypt HTTPS traffic is not enabled, enable it and see what is shown in Protocols. If you do not see tls1.1;tls1.2, then click on the protocols and add the below line in the pop-up.
Click OK. Ok again. Then restart fiddler for changes to take effect.
Now all the further requests that you make from Fiddler will have TLS1.1 and 1.2 support.
Hope this helps!