To participate to the challenge in steps or in km, all you have to do is authorize Meeriad to access your health data.
If you are using an Iphone, you have to authorize Apple Health.
If you are using an Android device, then you have to authorize Meeriad to access your Physicial Activities data. If you have a Google account, we highly recommend that you also authorize Google Fit to improve the data reliablity.
Your authorization is requested when creating your account. If you have not accepted the sharing at this moment, you can also accept the sharing in Profile > Settings > Data privacy.