I was looking for this myself and just figured it out. Its rather simple.
Open the file: wp-dm-albums.php and go to line 788. You will find the following function here:
function dm_manage_dmalbums_metabox()
{
if(function_exists('add_meta_box') && current_user_can('upload_files'))
{
add_meta_box( 'dmalbums_manager_id', __( 'DM Albums Album Manager', 'dm_albums_textdomain' ),
'dm_manage_albums_box', 'post', 'side', 'high');
add_meta_box( 'dmalbums_manager_id', __( 'DM Albums Album Manager', 'dm_albums_textdomain' ),
'dm_manage_albums_box', 'page', 'side', 'high');
}
}
The add_meta_box function will insert the DM Albums where you want it. As you can see in the code here, it is currently set to display in 'post' and 'page'. All you need to do is add this line before the first add_meta_box:
add_meta_box( 'dmalbums_manager_id', __( 'DM Albums Album Manager', 'dm_albums_textdomain' ),
'dm_manage_albums_box', 'YOUR POST TYPE NAME HERE', 'side', 'high');
Change "YOUR POST TYPE HERE" to the name of your custom post type and you are good to go.