When your employer sets you up for Sage HR, you will receive a welcome email inviting you to use the service. This email allows you to set up your access to Sage HR.
If you've not received an email yet, there are some things you should check.
Has your employer sent a welcome email yet?
Check with your employer that they have sent the welcome email - if they haven't then this will be why you have not received it. If they have then this indicates that either your email security is blocking the email, or the email address your employer set you up with is wrong.
Is the email in your junk/spam folder?
Have you been set up with the correct email address?
Check with your employer that they have entered the correct email address for yourself when they set you up. It could be that the email address they entered has a typo, or they used an alternative email address.
If you have made all these checks and can't see why you don't have the welcome email, inform your employer so they can contact support to look into it.