Winchester 1887s don't have a loading port in the conventional sense. Like another of Browning's shotguns, loading and ejection are through the same port.
To load, first open the action by operating the lever fully forward. Depress the shell lifter to the bottom, exposing the magazine tube. Then press the shells into the magazine tube past the shell stops, as with any conventional shotgun. After filling the magazine and closing the lever, the lever must be fully cycled again to feed a round into the chamber. Alternatively one can feed a round into the chamber and close the chamber. These new 1887s can operate with a round on the lifter, similar to an older Benelli, giving it a capacity of 7. (ie 5+1+1)
Sounds awkward, but this was state of the art technology in 1887.