The partition tables page can be accessed via the hosts menu:
Hosts > Partition tables
In order to provision new hosts using orcharhino, the hard drives (virtual or otherwise) that those hosts run on need to be appropriately partitioned. The partition tables page houses the templates needed for this partitioning.
In general, a clean install of orcharhino will come with any required templates, and it is not expected (nor recommended) that orcharhino users manually edit any templates. Locked templates should not be changed, otherwise they will not be updated any more. Use the clone function instead. Note, however, that cloned or self-created templates are not updated during an orcharhino update.
In case you know what you are doing, and template editing is desirable, the web interface provides extensive tools to do so, including inbuilt documentation on template syntax.