Allow access to add quotes only for Administrator

Hi,

Plugin is working fine and I found two limitations

1. Shortcodes cannot show “Next Quote” button in posts/pages – I solved this issue by creating a new shortcode in my theme which returns

quotescollection_quote( array( 'tags' => 'tag1,tag2', 'order' => 'random', 'echo' => false ) );

2. All my editors and authors have access to publish new quotes without any approval. This should be restricted. How can I do this?
Can you guide me which part of plugin code should I change to do this?

Thank you.