Adding files is simple in Fleep. You can either drag-drop the file into the message area or click on the + icon next to the message area and find the file from your computer. You can add more than one file at a time.
Please note that if you add files to the conversation together with a message then the two of them are linked together. This means that if the same message is deleted, the file attached to it will also be deleted. It also means that if you decide to pin the same message, then the file will also be included in the original pin. They belong together.
If you decide to delete the file from the File Drawer or straight from the conversation flow, then this will not affect the message that was added together with it.