1st year Ph.D. student in Computer Science - want to switch fields
First of all, it's better to make the exploration now than later. Having a good place to apply your CS knowledge can be very powerful, and now is a better transition time than you will ever receive in the future.

With that said, there are several bioinformatics courses online that you can try out; one popular one is Coursera. This allows you to spend a few hours per weekend exploring the topic from a well known professor, and can help you decide whether or not you are truly interested. From there, as @ff524 stated, it is best to ask your advisor for information on how to continue applying your skills to both your PhD and bioinformatics.