The currency codes for the GLOBAL currencies are set in DAC configuration. See section "3.1.2 How to OCnfigure Global Currencies" in the "Oracle® Business Intelligence Applications Configuration Guide for Informatica PowerCenter Users Version 22.214.171.124 " manual if you are on 126.96.36.199 or 2 or the same section in the 188.8.131.52 version of the manual if that is appropriate.
This goes through how to set your Global Currencies so they are populated correctly in the datawarehouse.
For example if you set Global1 to be EUR then your Balance Global1 Amount --> Facts - GL Balance presentation column will be in EUR.
Alos in ither financial SA's the GLOBAL1 amount is used as the amount e.g. AP Amount -> Facts AP Transactions. If you look at the Logical source for this it's computed from the GLOBAL1 columns.
I just checked in 184.108.40.206 and the GLOBAL2 and GLOBAL3 physical columns aren't mapped to any logical columns so you will need to map these yourself.
I would use the GLOBAL1 column that you are insterested as a guide to mapping the global2 and 3 columns.
To see what Logical (or Presentation) column(s) a physical column maps to find the column in the Physical Layer and right click. Select 'Display Related' then what ever related type of object you want.
This brings up a form with related objects which you can select and click 'Go To' in.