Clicking the offer-button in the email you received should direct you to your account page. Within a few seconds, a pop up will appear allowing you to apply the offer to your account.

Not working? No pop-up? Here's what you can do to fix it:

Refresh your browser tab and try again. Sometimes it takes a few seconds for the pop-up to load!
Disable any pop-up and ad-blockers or settings that may prevent redirects:
- Google Chrome: Go to Settings > Privacy and Security > Site Settings > Pop-ups and redirects > Allow.
- Firefox: Go to Settings > Privacy & Security > Permissions > Block pop-up windows (uncheck this box).
- Safari: Go to Preferences > Websites > Pop-up Windows > Allow.
If that doesn't work, clear your browser settings and cache.
Try a different browser or an incognito/private browsing window.