If you look in the FTP Partners of Efficy (R7987) in the folder /Efficy CRM/Efficy 10
there is the build notes in PDF. In this document all the information to install the multicurrency in Efficy is explain.
The different mode are also explain there.
The only thing that is not explain, is that it exist in standard a serverscript that you can schedule and that will get the Exchange Rate automatically. This script can be found in the wwwroot of Efficy since Efficy 10 SP1 : R8930 in the folder : efficy\serverscripts
It is called "CurrcyRates.js"