From the WordPress dashboard click on 6storage -> Settings.

After selecting the Settings you will land on the Tenant Portal Settings page.

To customize this display click on Feature Customization.  There, you will find Fields, Additional addons & other operations.

Disable:

By disabling the reservation option, the reservation button will not be available on the tenant portal.

Tenant portal:
 
 As you can see, the reservation button is not available.

Enable:

By enabling the reservation option, the reservation button will be available in the tenant portal.

Tenant portal:

 As you can see in the below image the reservation button is enabled