multi factor remote access

Hi,

In setting up a  fortinet based multifactor setup, fortigate firewall is used along with Active directory.

Now, to enable the second factor (token) what configuration is required on fortigate considering that an AD is being used.

We have tried looking at documents available online, but all of them indicate two factor with local username password & none with an AD being used.

Please help  with some links or help regarding configuraing this for second factor (token) authentication with AD radius.