The Bulls are offering a presale of tickets on Sept. 29, ahead of the general public sale on Oct. 1, to anyone who signs up for the myBulls email newsletter.
↵You can do that here. Details:
↵This is your exclusive opportunity to buy Chicago Bulls tickets before they go on sale to the general public. Your presale begins on Wednesday, September 29 at 10:00 a.m. and ends that same day at 9:00 p.m. You can guarantee yourself seats to the most popular games before they are sold out.↵
There are a couple of other methods listed on that page, but the email newsletter seems to be the easiest one.