Does anyone have any idea how this can be done?
I`ve read about it on websites, but I don`t really understand how to actually carry out. If you do know, I would be very grateful for your help =) Thanks!

What a lot of people don`t realize is that you don`t want to breath circularly. Breathing with the music in rhythm helps you to keep a steadier tempo and feel the music better.

unless you are ok with ending up on the floor a couple times from head rushes.. or ending up in the hospital.. I dont really advise circular breathing.. it gets... menotinous.. lol

hey.
in australia (where i`m from) the aborigines play this thing called a didgeridoo. Well it turns out that these guys can play for like 10 minutes without seemingly taking a breath (i`ve seen it happen). So i checked up on it.
Basically, (it takes a lot of practice) you have to practice filling your cheeks with air, and closing your throat. Then blow the air out using your cheeks (i suggest swallowing to close your throat). Then you just have to learn to take a breath through your nose, while you`re blowing out using your cheeks. It takes a lot of practice.
My band director saw a girl do 30 measures on oboe with circular breathing. You need to practice a lot to get your embochoure right.

My band director mentioned using a straw and a glass of water to practice on.