If you have checked the option 'Everyone' when sharing, those you share your album with can view it without loggin in or registering. The link opens on any device, no need to install an app.
If you choose 'Private', visitors are required to log in/register at MyAlbum. Share the link including the access code. After the visitor has logged in, they enter the access code once. They can now view the folder or album when they are logged in.
You can revoke that access and change the code at any time. This way you always have control over who has access to an album/folder and who doesn't.