I had created a Partition on my iMac for Sierra OS to test Sierra OS with my apps before buying the new MacBook Pro laptop. I can't get rid of my El Capital partition now on my iMac. (Another story). I fubarred my time machine backup, erased the content on my El Capitan volume (hoping to delete it, which I can't). I've tried restarting with a recovery volume. That doesn't work either. Setting those issues aside, how can I use my iMac Sierra partition/startup disk with migration assistant to my new MacBook Pro. I get an option to only migrate my entire iMac, for which I get an error on the MacBook Pro saying there is not enough room. I don't see an option to migrate from my Sierra startup disk which I have booted from to start my iMac. I'm using the network connection for migration.