There are a lot of videos on youtube that show you how people open their chakras. I would suggest on meditating on each area, visualizing the color associated with that chakra. Start with your root chakra and work your way up feeling the energy travel to each one. I wouldn't try the Ouija Board until you felt comfortable and open to it. Not to say that it wouldn't work in communicating but, i think you would have better success once you've meditated a bit and opened yourself up.
I personally don't meditate more than 5 minutes on each chakra. But, then again i can feel the energy move from one to another fairly quickly. It would be up to you on how long it takes. I wouldn't exhaust myself, but rather find a comfortable relaxing place to work on it. I would check out the videos though, there might be something on youtube that suits you better...
Chakras are never fully closed ,they are simply opened to a different degree.Having chakra too wide open also causes disbalance ,within it's counter chakra.For example having upper chakras too wide open will cause disbalance in Root and Sacral ones ,and as result you will not be able to ground very well.
If there is imbalance within you I would rather suggest that you fix this before attempting any communication with spiritual entities, especially in so random manner as with the board.
We attract what we project ,so if I am projecting happiness and balance most probably negative entities will not try to have a go on me.And even if something not so jolly approaches me they probably will come for help, not to attack me.
It is hard to attack something that is in balance in any single aspect of it's existence.
your chakra's don't have anything to do with a ouija board with the possible exception to helping the energy flow and becoming more aware of your surroundings. what's more important is knowing how to cast a circle, cleanse, protection spells, and how to work the board than chakra's being open or closed.
Not to discourage you are anything, but I wouldn't advise using a Ouija board for anything. I have used one in the past and I am still trying to get rid of the things that came out of it. I used the board like I was suppose to and still it was bad. I will never touch one again. Just my opinion though. I don't want anything bad to happen to you.