Few Gateway configuration need to be done using CLI or some backend files need to be edited or for any CLI based operation we need terminal, Hence same as NodeRED you can click on Terminal icon and it will open terminal in new tab or you can directly open in browser by "<gateway_IP>:7681"

After clicking icon terminal will open in new tab and ask for user/password , it's same as gateway login

Credentials --> user/pass : root/root

Now CLI utility can be used for any specific purpose.