It works on the PC version as follows
Route - Open
at the bottom of the pop-up select "Open from a different location or with a different file type"
On IOs you cannot import the file from within Skydemon.
You need to have access to the file on your machine (via Files, attached to a mail, shared on a drive ...).
You click on the file, then the Share icon and then Skydemon (might be hidden under ... More).