The 'Bill Of Material Replacements' module allows you to replace 'Raw Materials' and 'Consumable' items on 'Bill Of Materials'.
Navigate to 'Production' > 'Maintenance' > 'Bill Of Material Replacements'.
Click the 'Add New' button at the top left of the screen to add a new 'Bill Of Material Replacement'. 
On the 'General' pane select the 'Company' and 'Branch' from which you wish to edit BOM's. You can also add a 'Reference' for further detail.
On the 'Replacement Details' pane, select 'Inventory Code' and 'Replace Inventory Code'. The 'Inventory Code' will then be replaced by the code selected as the 'Replace Inventory Code'.
Click the 'Find Bill Of Materials Used' button.
This will fill the 'Bill Of Materials' pane with a list view of all BOM's containing the 'Inventory Code' to be replaced.
In the 'Replace' column, check the boxes for the corresponding BOM's you wish to edit.
If you check the 'Default Replace All' box in the 'Replacement Details' pane before clicking the 'Find Bill Of Materials Used' button. then all BOM's found will automatically be selected for replacements.
Once your BOM's have been selected, click the 'Replace Inventory On Bill Of Materials' button.
Paradigm will prompt you if you are sure you would like to make these changes to the selected BOM's. Click 'Yes' to continue.
The status of the 'Bill Of Materials Replacement' document will then change to 'Completed'.