I cannot write in the Outgoing mail Server box and my ICloud mail account does not work on my mac, but it does on my iPad please help

You don't input the information in manually for iCloud mail. It is automatically set up for you when you sign into iCloud via System Preferences and choose the Mail checkbox. Sign out of iCloud or deselect Mail in iCloud preferences. Open Mail's preferences and choose accounts tab. If iCloud account still exists in the list, delete it. Sign back into iCloud or check the box for mail. The account will be auto created for you.