After you have claimed or activated an Earning Rate Bonus, you can see whether or not its active and what multiplier its using by navigating to your Earn page of the application at the top. On this page you can view your Earnings summary, where your earnings multiplier will be shown on the far right at the top.
By hovering over the information tooltip, you can access further information about your bonus, including how much balance has been earned using it, and the total amount you can earn from it.
This tooltip and Earning Bonus icon will only show on Bonuses claimed during Seasons or other rewards, and will not show from your referral code being entered. Your referral code progress will continue to appear in the Referrals page of the application. You can read more about this here.