Why do you need to import SqlEnum namespace? Which type would you like to use from it?
I cannot find any documentation for this namespace on internet, so I guess it really doesn't have any public members (as the warning says). Therefore there is nothing you can use from it and you should not import it. If you just need to use some other type from different namespace in Microsoft.SqlServer.SqlEnum.dll, then you don't need to add it into Imports. You just need to add that DLL into your project references.
Did you try just delete that import line?
Also note that this is just warning, it is not an error, so you should be fine with 'just' ignoring the warning.
BTW: This questionseems tobe VB.NET question as there is nothing SSIS specific - please use VB.NET forums for similar questions. This forum is dedicated for building tools for .NET developers like profilers, debuggers, compilers, etc. (see sticky post of this forum).
-Karel