If you are creating a new account, then you will be asked for your consent at the point of signing up. If you already have an account, then you can update your preferences within your account.
Providing consent for your details to be shared will give the charity permission to contact you via email, for example about fundraising or news.
Please be aware that if you choose not to give consent, you may have agreed for your data to be shared via another means (either directly or via another organisation).