1 - Go to the Properties menu and select Buildings.
2 - Select the Building that the Unit you would like to create an Activity for resides in.
3 - Select the 'Activities' tab.
4 - Here you will see all the Activities for this Building, as well as for all the individual Units within the Building. Click 'Add Activity' to create a new activity.
5 - Fill in the 'Activity Overview' details, but do not click the blue search button next to 'Unit' and select a specific Unit within the Building. The building will be automatically selected, so you do not need to change this.
6 - Click 'Save Activity' when complete.