There is a very thorough guide that includes using RigPi with the IC-7300 in the files section.
It may be overly thorough, but all of the information is there:
There is another guide too, with fewer details:
There is also a thread by Howard at:
There are a number of message threads on the IC-7300, you can find them using the search tool at the top if you use IC-7300 as the subject.
To answer your question directly would require a tad more info from you.
Which program are you asking about downloading?
If it is Plumble for the Android (that is the Android version of Mumble) you go to the Google Play store and download it from there.
Same for VNCviewer if that was what you are asking about.
Lots of folks ready to help.
73 - Mark - K8MHW
'A RigPi Enthusiast!' - I am not otherwise affiliated with MFJ or RigPi