Download the file to a directory.
Open BeerSmith
File > Open File
From the dropdown extension menu, select "Beer XML Files (*.xml)
Navigate to the directory with the xml recipe
Highlight File > Open
The recipe will show in a separate tab with the file name as the title. To keep the recipe handy, copy and paste it into a folder in the "My Recipes" tab.
More complete information can be found in BeerSmith help under Importing and Exporting Files.