You can share levels created in the editor through email or iMessages. When you're done testing your level, click the menu button (upper left corner of the editor), and select "share level". Select email or iMessages and then fill out the email or iMessage pop up.
Your friend will receive a message with a .happywheels file and
a message containing a link to the App Store in case they do not
already have Happy Wheels downloaded. When they tap on the file,
they may see what looks like a bunch of code. They should then tap
the button in the lower left corner that looks like this:
If they have Happy Wheels installed, they should be able to open the file in Happy Wheels.