ADSL broadband is compatible with WiFi. As it is a contended service shared with other users, the best WiFi performance will be during off-peak hours and for basic tasks such as checking email and loading web pages.
To use WiFi with your ADSL broadband connection, you require a modem or router, such as the common ones found in most homes and offices. Once this has been setup and configured, you should be able to use WiFi by connecting your chosen device or devices.
*Devices must have WiFi functionality.
Essentially, while WiFi is available to use, the signal will be weaker than if you were connected to a high-speed, uncontended broadband service. It may only work well on one device at a time, depending on how you are using it. For example, the more one device is downloading, the slower another connected device may perform.