Guangyan Guo : Currently, if you are using Studio Trial instance then the ThingWorx 8.0 instance is setup by us automatically. You do not have to install ThingWorx and is done/created for you by our R&D team on cloud.
I believe you are looking or want to connect your local ThingWorx 8.0 instance with ThingWorx Studio. For this, you will have to setup your own local Experience Service. Please refer and follow if you have access to this documentation - http://support.ptc.com/WCMS/files/173159/en/TWXESInstallDeploy.pdf