You create a gallery and your other team members don’t have access? Please contact the account owner – he/she can manage the access for all galleries for all team members. This way, each team member does not have to take care of it individually – and no one can accidentally remove existing access rights for other Team Members.
Details about the different permissions can be found here: What is the difference between the access rights for Team Members?
How do I share galleries with external customers and service providers?
Create a secure or clear link for the gallery in the gallery settings and send it to the people who should get access. External users will only get access to this gallery (and subgalleries). For them you can set in Gallery Settings > Functions what exactly is allowed in the gallery for external users: downloads, comments etc.