The homepage banner, construction page banner and the Rentals page banner are updated the same way. These pages are modular pages where the page is built from a series of different modules. The top module that contains the banner is called a Showcase.
When you log into admin, access the "Pages" section by clicking on it from the left sidebar menu. Expand the home page node, it will expand and look like this:
Once you have expanded the node for the home page, you can see the four modules used to build the home page. The one titled Showcase is the module for making the banner. Click on Showcase to edit it.
