Q: how do I piggyback my airport express to another airport express to extend the range?, how do I piggyback my airport express to another airport express to extend the range?

First, you must already be using an AirPort Express as your router.

Then, configure the other AirPort Express to "extend" its wireless network.

Pictures from Wi-Fi base stations: Setting up and configuring an extended wireless network (802.11n) follow. The remainder of the article is less helpful since it discusses an earlier version of AirPort Utility.

Read the link at the end regarding a factory reset. Do that and then launch AirPort Utility. The current version will configure your network more or less automatically.

The pictures show two Extremes but the Express is similar.

Set up: Components of an extended network

➊  Primary Wi-Fi base station (this is the base station connected directly to the Internet)
➋  Extended base station

Configuring a wireless extended network

To create a wireless extended network, you must place any extended Wi-Fi base stations within range of the primary Wi-Fi base station.

Start with the device that will be configured as the primary Wi-Fi base station.  Then configure your extended Wi-Fi base stations, ensuring that each is within direct range of the primary Wi-Fi base station.The physical location of extended Wi-Fi base stations will vary according to the building environment and may require some experimentation.

If you have configured your Wi-Fi base stations in the past, it may be helpful to do a factory default reset of each Wi-Fi base station that will be part of the wireless extended network before you begin.