Help for Blender

[shmulikhazin]

When I bring up what I created for Second Life

There are parts of what I made transparent

What to do

[Rolig Loon]

You have flipped the normals on those faces, so they are turned the wrong way.  Go back into Blender and flip them the other way.  When you are creating in Blender, it is always wise to turn on the Backface Culling option so that you can see when you hav make this mistake.  You can also choose to display the face normals themselves, which serves the same purpose.