In object mode the asset loaders, located in the Pie Menu, are used to append Decals from your Decal libraries, or Trim Decals from your Trim Sheets to the current scene, a process performed by the Insert tool.
By default Decals will added at the location of the mouse, at the time of opening the pie menu.
This can be changed in the main Panel.
Various Decal libraries, represented by Asset Loaders in the DECALmachine pie menu
Using the Asset Loaders + Insert
Using Batch Insert
CTRL + D
To quickly bring the same Decal into the scene, that you've appended previously, Quick Insert can be used, thereby skipping the Pie Menu completely.
Edit Mode/UV Editor
Select one or multiple faces.
In edit mode or in the UV editor, only the registered Trim Sheets will appear in the pie menu.
Instead of appending Decal or Trim Decal objects via the Insert tool, clicking on the plus button or thumbnails will run the Unwrap Trim tool.