1) Create the bottom floor with iron blocks. An elevator can be as small as 1 block or as big as 15 blocks in any shape. Smaller areas will have less lag. Make sure the lift iron blocks don't touch any other iron in the building -- the plugin doesn't know the difference!
2) Next create the floor's control panel. On a wall place the following blocks. The signs and buttons must be "over" one of the iron base blocks.
3) Create the elevator shaft. To create a new floor platform use glass blocks instead of iron. Like the first floor over one of the glass blocks create the floor interface.
4) Make sure the shaft is clear of all obstructions except for floor glass, buttons and signs. Torches and vines are also allowed in the elevator shaft.
5) To use your elevator right click the sign above the button to select a destination floor. The sign will automatically add the correct information.
Video Tutorial: https://www.youtube.com/watch?v=k-IT_ULndbE