A web address will be in the format www.google.com.
Sometimes people may just put google.com with no www in front
And sometimes they put "http" in front like
http://www.google.com
You need to open a browser (if you have Windows then Internet Explorer is installed by default).
Then in the "blank" area at the top put in the web address.
That will take you to the web site.
Then on the web site there will probably be a "contact us" section where you can find the email address to contact the company.
Write down the email address and then send them an email.