Use the below Url fro reference.
In FDM Workbench client--
Create application, Import Adapter for Essbase, Register application , map dimension.
In FDM Web client -
Create Import format, Create Location , do mappings etc.
Let me know if that helps or please send me your email address i will send you complete step by step doc.
Are you referring to import data from Excel Trial Balance template provided by FDM? or do you want to import data from a csv file?
The process is the same but you need to take into consideration that if you use the Excel TB template, the import format will not be applied.