How do I stop posting on select or all accounts?

Simply go to Settings tab for the account you want to disable or remove. Use the "Status" field on this page to 'Disable' or 'Remove' the account(s) and all posting will be paused/stopped on the account(s). 'Disable' will allow you to re-start posting anytime, by activating the account from the same drop down in the Settings tab. If you 'Remove' the account, the account will be removed completely and to re-start you'll have to re-connect the account using 'Add Social Account' button on the top-left.