How to add files to a collection
On the Collections page:
First, click on the collection you'd like to add new files to.
Then, click on New Collection.
Next, click on Add from Library.
In the library, check the files you wish to add to a collection.
Next, click on Manage collections.
Check the collection you wish to add the files to.
Click on Apply.
You can also add files to collections directly from the Library without opening the Collections page first.
The added files will now be marked with the specific collection tag so that you can easily see, which collections your files belong to.