I don't know which tutorial you are talking about, might be an old one.
But currently you don't have to delete anything or re-add anything.
By the way, all runtime libraries are in the <RuntimeLibraries> folder under the root of the LLBLGen Pro installation folder (Categorized by the .NET framework).
e.g. C:\Program Files\Solutions Design\LLBLGen Pro v2.6\RuntimeLibraries