Before a user is able to badge into a door an Access Admin must first grant them access to the door. In order for a door to unlock it needs to be assigned to an access level and that access level needs to be assigned to an access group that the user is a member of.
You will need to have Access Admin permissions
You will need to have Site Access Admin permissions for the site containing the door(s)
Ensure you are an Access Admin
If you add an access controller to your org you are automatically made an Access Admin. Otherwise, another Organization Admin (or your account if you are an admin) needs to go to Admin > Org Settings > Users to elevate your permissions.
From the Users page, select the account to be modified and edit the role dropdown to the appropriate role.
Ensure you are a Site Access Admin
Site Access Admin permissions allow you to see the access controllers and doors on your Home and Devices pages. If you are an Org Admin, you can give yourself Site Access Admin permissions for any site. If you are not an Org Admin, then a current Site Access Admin for the site with the door in question will need to make you a Site Access Admin.
To do so, go to Admin > Access Control > Access Sites
Select Admins in the row for the site you wish to grant Site Access Admin
Next, click Add in the top right
When the dialog box appears, find the user in the list, check their name and select Done to make them a Site Access Admin
Assigning a Door to an Access Level
Navigate to the door's page and select Access
From here, select + Add Access Levels to see a list of all configured access levels for this door. When the dialog box opens, check the box for the desired access levels to apply them to the door and select Add.
Assigning the Access Level to an Access Group
Navigate to Admin > Access Control > Access Groups
Select an Access Group
Select Access Levels and + Add Access Levels
Check the box next to the access level the door was added to then select Add
Assigning a user to the Access Group
From Admin > Access Control > Access Groups, select the group to add a user to. On the right side of the page select + Add...
Check the box next to the user(s) you want to add to the group and finish it by selecting Add.
Upon completion of the above steps, the user will be able to unlock the door.