I brnched the question into a separate thread, so that others can easily find it.
There are two ways with different objectives:
1. Import your own database
Indeed you can create your own database and import it into the Toolbox. You will find all the necessary guidance on how to do that here:
You can then use the database like any other database in the Toolbox.
2. Adding your own descriptor
Most descriptors based on phys-chem properties in the Toolbox are calculated, e.g. with the EPIWIN modules. Youcan also load your own experimental data and use them as descriptors. You'll find guidance on how to do that here:
Hope this helps