how do i delete multiple emails in macbook

No problem - just quite a difference between the laptop and the desktop "workhorse" Mac Pro....

I just sent myself a test email to show you - in my example, I am showing the Sent folder:

Just highlight the email and hit Delete (or use the delete key on your keyboard). If there is more than one, highlight the first one, hold Shift key and highlight the last one you want to select - everything between those two will be selected. Hit delete and they're gone. Don't forget to empty the Mail trash occasionally...

Delete MULTIPLE ( ALL email)

1- move mouse to any email hit " LEFT" button ===> see BLUE highlight

2- "COMMAND" + " A " ==> select all email become =BLUE highlight

3- move MOUSE to " TRASH icon" on the top = will delete ALL email

4- move MOUSE to " TRASH icon" on the BOTTOM right ===> hit "EMPTY"

Where are the emails (in what application: web based/accessed via browser or Mail.app or some other mail client)?

And, is this on a Macbook or (per your profile) a Mac Pro (which is not a laptop)?

Try Mail/Preferences/Accounts/Mailbox Behaviors/Trash and check Move deleted messages to the Trash mailbox. This must be done for each account.

Delete and command - delete do the same thing.