To sign and provision your Xamarin iOS solution, you should first upload your .p12 certificate file and .mobileprovisioning profile through our portal ( > Agents > My Agents > VSTS Agents > Actions (next to the agent) > Upload

Next, in your Microsoft VSTS account, "signing and provisioning" setting under the "Build Xamarin.iOS solution" step:

1. Select the "identifiers" radio button.

2. In the "Signing Identity" field, input "iPhone Developer" or "iPhone Distribution" depending on  which signing identity you wish to use for signing.

3. In the "Provisioning Profile UUID" field, input the UUID for the .mobileprovisioning file you have uploaded.

4. Queue your build for signing using the specified signing and provisioning identities.

Please contact us if you have specific questions regarding signing and provisioning.