Open up the Breiss malts .bsmx file you downloaded. Find the malt you want to copy to your ingredients profiles. right click on that malt and select 'copy'. Now open up your fermentables folder. Right click on the list of ingredients and select 'paste'. The malt you selected will be copied into the ingredient library.
Note: if you are on an Apple and are 'right-click' challenged, you can also use the 'copy' and 'paste' in the toolbar.