A substance can be linked to a space from two location: from the Substance module and from the Spaces module.
Go to [Spaces] in the menu. Select the space to which you want to add the substance by clicking it in the grid. To add a substance, first click the pencil icon to enter edit mode.
At the bottom of the page, under the Substance tab, click [New] -> [Maximum stock]. A new window will open.
You will see the following screen.

When you add a substance from within a space, the selecterd space is shown in the 'Space' field. If necessary, you can search for and select a different space by clicking the search icon, selecting the correct space from the list, and clicking it. You can add the substance in the same way. Next, enter the maximum stock quantity for that space and select the unit in which the substance is registered.
Confirm your entry by clicking [OK]. You will return to the main screen, shere the substance is now listed at the bottom of the page uder the 'Substance' tab. Finally, confirm your changes by clicking [Save] at the top of the page.
See the work instruction Linking a substance to an article, department, room or person.