Best to take it to a gunsmith and ask for help.
You should be able to download a manual at Browning's web site.
100yrs give or take
If you don't have an owner's manual, take it to a gun smith.
Go to Browning.com and you can download a manual.
Loading a pump-action shotgun is fairly simple. Open the action and hold the stock underneath your arm. Pop a shell into the action, then close the action to load your chamber. To load the magazine tube, take the next shell and push it into the action, then pin it in place using your index finger.
You can get the manual from this page with some basic info. http://www.winchesterguns.com/services/index.asp
Need to know who made it. Need to know if it is a bolt action, pump, or semi-auto. Does it have a model number on it?
Which one?
Best left to a gunsmith
Your really should take it to a good gunsmith
Read the owner's manual or have a gunsmith do it.