There are just a few things that i would like to ass to this subject.
The third eye chakra or the 'sixth chakra' as we tend to call it from time to time, is pretty much a confusing and not understandable chakra to work with if you haven't already started with a basic establishment with chakra work. It is always very suggested and highly recommended for any person to firstly begin working with their root chakra and keep working up to develop a basic establishment that will support your higher chakras while the third eye chakra/ sixth chakra is one of them.
While most of the people including the person who posted a link to meditation will suggest you to perform meditation on the spot, I don't suggest it for your third eye development if it's about performing it on the spot. For different people (may include any particular person) it can take time and patience to learn a good method and develop modifications that work best for the individual person. I would usually tell someone to learn about the demands or additional recommended constituents for practice before jumping into this particular practice.
Meaning you should be able to meditate in a general way before trying to open your third eye and attempting to perform meditations that are designed specifically for chakra work including the third eye chakra.
I suggest you to at least know how to generally meditate first before attempting to perform any specifically designed meditations, no matter for what, including the chakra meditations, as I told you already.
These are my two cents to the topic.