Kindle – kindle app file transfer to kindle

Hi, I’ve done a search in the forum for this but cannot find the answer I’m looking for.
I’ve recently bought a kindle and have a number of e-books in mobi format that I’d like to read on the kindle. They open in the ‘Kindle for Mac’ app, but then I cannot figure out how to transfer to the kindle. Any ideas much appreciated?
PS Sorry if this has been asked elsewhere on the forum – I did look!
Answer #1
calibre works for me
Answer #2
yes calibre is the one