On the top right drop down menu under your name, click the option labeled "Inventory." You will see your current inventory. Click the green "Add a new bike" button and follow the prompts until you have filled everything out.
To edit your ride. Go to "Inventory" and you will see the "Created" tab. Click that and on the right side of the ride, there is a drop down menu labeled "More." Click this and you will be able to choose from a list of options to edit.