3rd-party certificates in FR3

[Иван Стрельников]

Hello everyone!
I'm using freeradius 3.0.9.
And i want to realize next scheme:
cisco wlc wi-fi -> freeradius -> mysql db.
It's all ok with db, i just want to clear out the messages to end user
about radius certificate.
So, i want use a certificate, which root ca will be in apple\android's
certificate stores.
Maybe geotrust, maybe other.
I didn't find how it should to install and i need help here.

Thank you.

tl;dr I need a cookbook how to setup chained certificate from other
trusted root CA.

-- 
BW, Ivan.