How to add to the transfer queue?

I have checked the Knowledgebase and have not come across an article explaining how to do this. I presumed a simple click and drag of the files would allow for me to add to the queue but apparently that isn't so. I've tried adding files one-by-one using the 'Add' button in the toolbar but still, I have no luck. I have also tried the 'Add to Temporary Queue' in the Right Click options but again, no such luck.

So my question is: How does one add to the Transfer Queue, please?

oOo Thank You