The best way to find jobs as a security officer would be through your local job ad website. It could be wowjobs, kijijji, or even the gov job website. When security jobs are posted it means they are hiring.
The ministry is required to post every company in Ontario that is licensed to sell security services. You could go through the list and apply to every company.
The best way would be to find security companies with local offices in your city and visit them in person with a resume or to e-mail a resume to the company online.
REMEMBER no security company will hire you to be a Security Officer if you do not have a license. There may be other oppertunities in the company but you will not be allowed to do security functions without a license. To get a license you have to take a training course and a test go to www.ontariosecuritytesting.com for more information.