How can I get my iMac top line browser to appear?

What version of OS X is installed on the computer? Without basic information such as this helping you is extremely difficult. If you don't know the version of OS X that is installed, please click the apple symbol in the upper left of your display and then click About this Mac.

By top line do you mean the one with the URL window. Go the the View ➙ Customize Toolbar menu

and then see if you need to add the URL window to the top menu bar in Safari.