Working with a BQ4285 RTC from Texas Instruments
The device you've come across (presumably from an old PC motherboard or similar?) is likely to be a poor choice for interfacing to an Arduino from a practical point of view. It's designed to interface to a microprocessor with an external data bus and after a quick look at the data sheet you'd need to use 8 I/O lines for address / data information and at least 4 others to clock data in and out of it.

While it may be an interesting experiment if you're not comfortable with its operation you might be better to looking for a device such as the DS1307 on e-bay for a few dollars. Many come on small PCBs with a backup battery and crystal in place and are in an Arduino-friendly format.

Devices like those only require a couple of I/O lines and there are many libraries and examples already available. For example see DS1307 RTC With Arduino.