I recently bought a full tang katana and i would like to sharpen it. it has what looks almost hexagon shaped blade. any tips to get sharp?

My advice would be that to start with, don't.

There are a lot of videos around about sharpening knives. Watch a few dozen of them. Then get a few knives that you don't mind ruining and practice on them. When you have that down, watch a few dozen of the videos around about sword sharpening, pick a method you like and have the equipment for, and proceed carefully from there.
Be aware that the first few attempts will almost certainly be less than perfect, and may adversely affect the blade you are sharpening. With that in mind, if you really like your new sword, don't learn to sharpen on it, get a cheap and nasty replica and make your mistakes on that first.
I have been playing around with sharps casually for more than 2 years, and every time I sharpen a sword, I am surprised by the amount better it is than the last time, and embarrassed by how bad a job my first few attempts were and what I got wrong. There are plenty of folks with far more experience than me who will be able to give much more specific advice, but my 2c is to accept that you will make mistakes.

https://www.youtube.com/watch?v=vYkKfUSW1J8

This video might be of use to you. And as mentioned before, try to get some practice in on some blades you don't care about before attempting to sharpen one that you'd like to keep. I find that, when using a whetstone, swords are always more of a pain to sharpen than knives or daggers.

Thank you everyone for the replies. it helped a lot