We'll need a bit more information here. I'm assuming you don't mean the switches themselves, since they're pretty straightforward.
If you are talking about a block, such as one that is solid when the ON/OFF switch is ON, you'll need to download it from the Blocks section, and use Gopher Popcorn Stew, also known as gps, to insert the block into your rom. This can be found in the Tools section.
Once you download the tool, read the readme, and if you are still having trouble, this thread may be of use to you.
Could it be because you set the destination to the tiles the pipes are into? If so, relocate it to another tile (preferably the ones on page 2 of the 8x8 tile editor) so it doesn't bug anything you might want to use.