First thing's first: Log in to your Meetup Account
Before you begin, make sure you're logged into your Meetup account. This is important: any discount already applied to your Meetup account will only be reflected if you're logged in.
Head to the Payments Page
If you have been nominated to step up as Organizer of an existing Meetup Group, click the link in the email you received about your nomination. If you are returning to Meetup to finish creating a new Meetup Group, you'll want follow the link in the email you received as well.
If you are currently a Meetup Group Organizer, click on your profile menu in the upper right corner of the screen, and select 'Settings.' On the next page, click Organizer Dues. Then, click Change next to your current Organizer Dues plan.
Apply your coupon
If a coupon is attached to your Meetup account, you'll see it near the top of the form.
Click it, and the pricing for the Organizer Dues options should update to reflect the discount.
You may need to provide your billing information if you haven't done so already. When you're ready, hit the Next button at the bottom of the page. (Organizers applying a discount to an existing Organizer Dues plan will see Change instead of Next.)