I have created a custom field but only admin users can see it
Karen, welcome to CiviCRM StackExchange. 

Check user permission by navigating to CiviCRM >> Administer >> Users and Permissions >> Permissions (Access Control). Click on Drupal/Wordpress/Joomla Access control link(name is based on CMS you using). 

Check for 'CiviCRM: access all custom data' permission for the user role. If uncheck, check the option under the role and save the permission. This will enable access to all custom field in your system for that user role. If you want to restrict specific custom group being visible to user than you will need to add ACl for the custom group to perform CRUD operation.