I am a relative newbie. I have successfully created a test environment for a Samba4 active directory server. I also want to setup Freeradius on the same server for authentication of other services.

Simply put, I need help. I have searched high and low; found some slightly helpful links. If any body can point me in a good direction, I may have better luck.

Here's my test environment:
$ uname -a
Linux dc1 4.4.34-v7+ #930 SMP Wed Nov 23 15:20:41 GMT 2016 armv7l GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID: Raspbian
Description: Raspbian GNU/Linux 8.0 (jessie)
Release: 8.0
Codename: jessie

$ sudo /usr/local/samba/bin/smbstatus
Samba version 4.5.2

$ radiusd -v
radiusd: FreeRADIUS Version 3.0.13 (git #79c5409), for host armv7l-unknown-linux-gnu, built on Dec 26 2016 at 22:57:13
FreeRADIUS Version 3.0.13

What have you tried so far?

You can treat a Samba 4 AD DC like any other (Windows) DC, so all general tutorials covering Active Directory integration are relevant. I found several on the FreeRADIUS web site, and I'm sure there are many others.

Basically, you have three options: Authenticate using NTLM/winbind, Kerberos or LDAP. I can't recommend either over the others without knowing which RADIUS clients you want to authenticate.