There are many different private and government run organizations including us that provide ESL classes:
ESL classes may take place during the day, in the evening or on the weekend meaning you have a lot of flexibility. Whether you are in the workforce or education, there is likely a time slot that will accommodate you. However, some classes accept students at any time and others have specific start dates, so you should plan ahead. Also depending on the organization running the lessons, it may be free or cost money. You should contact organizations near you to find out if they have ESL classes, how to enroll.