Tell a responsible grown up, and leave the gun RIGHT where you found it.
Any gun store or major retailer should carry a fire proof gun cabinet. Also you might be able to find one in stock at amazon.com.
Get a manual from the maker or find a good gunsmith
Type in gun app you should find app by Felix khazin in app store
To find out what gun a bayonet is for, you should get on wikianswers.com and type in the info of the bayonet.
The nearest police officer or station you can find.
www.gunsamerica should be able to help
The weapon itself should be marked with the maker's name somewhere..
I would find it difficult to find out what type of gun you have.
Go to the Google website, and from the upper toolbar select IMAGES. On the search page, enter "airsoft" or "BB gun", and you should find hundreds of pictures.
In countries which have gun registration, such lists are made available only to law enforcement. They are not made available to the general public, nor should they be.
Use a temperature gun.
From what I could find your gun is made by Winchester. It should say it on your gun somewhere though.