As you have seen from this manual that ERPNext contains tons of features which you may not use. We have observed that most users start with using 20% of the features, though a different 20%. To hide fields belonging to features you dont require, go to:
Setup > Customize ERPNext > Disable Features.
Check / uncheck the features you want to use and refresh your page for the changes to take effect.
To hide modules (icons) from the home page, go to:
Setup > Customize ERPNext > Modules Setup
Note: Modules are automatically hidden for users that have no permissions on the documents within that module. For example, if a user has no permissions on Purchase Order, Purchase Request, Supplier, the “Buying” module will automatically be hidden.