Green Button 'Clone or download' then download the zip file.
You put the folder containing multiple files into your Arduino "sketch" directory/folder
.. on a pc it can be found under the 'file -> preferences' tab. I bet something similar on a mac.
Yes it may be a little confusing that there are multiple .ino files in one 'sketch'.
... and I'm pretty sure that the primary .ino file needs to have the same name as the folder in Arduino land.
Anyways, I put in a folder called "ubitx_v43" and renamed "ubitx_v4.3_code.ino" to "ubitx_v43.ino"
It compiled and linked, albeit quite a few warnings for someone so driven to clean-up :)