Draft the proposed new or amended by-law, submit it as a motion to a general meeting, and pass it by special resolution (75% in favour). Once passed, lodge the change with the state titles office or registrar so it appears on the strata roll.
By-laws don't take effect until lodged. Get help wording the by-law from the strata manager or a strata lawyer — vague or contradictory wording is usually struck down by tribunals when challenged. Always make sure the new by-law is consistent with state legislation; you can't override the Act with a by-law.
Compare written fee proposals from strata managers covering your building — free for owners corporations, no obligation.