Open the subdomain-1 node under the Regions node, then open the Boundaries node to see the boundaries that were imported with their default names. Right-click on the boundary-12 node and select Rename...
The Rename dialog will appear.
Change the name to Inner_wall and click OK.
Using the same technique as in the previous step, rename the other boundary nodes as follows:
This portion of the object tree should look like this when you are done.
