I am trying to find difference in usage between the words ラベル and シール. Could you please give some specific explanation and maybe example? I would be very grateful for your help.
A small sticky piece of paper is broadly called シール regardless of its purpose or shape (yes it's wasei-eigo). Cheap paper stickers used by children for decorating toys, photos, picture books or such are almost always called シール. If its main purpose is to convey some information such as prices, ingredients and addresses, you can call it a ラベル as well. 宛名ラベル and 宛名シール mean the same thing (address label) in Japanese, and they are equally common.
ステッカー in Japanese is like シール, but it tends to refer to more expensive, larger ones. Stickers made of plastic film or magnet sheet are usually called ステッカー but not シール. (But expensive large paper stickers are called ステッカー as well as シール) For example, some people decorate their cars with ステッカー, but not with シール.
By the way, record labels are called レーベル in Japanese for some reason. (This should be in this list...)