To sign and provision your Xamarin iOS solution, you should first upload your .p12 certificate file and .mobileprovisioning profile through our portal (portal.macincloud.com) > 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 how which identify 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 to signing using the specified signing and provisioning identities.
Please contact us if you have specific questions regarding signing and provisioning.