How do I pass parameters from veiws to controller in Ruby through routing in routes.rb?

I am working on a product selling/exchanging project in Ruby where on the homepage you can see all the products up for sell, and exchange. The user who posted the product can be viewed through a link to their profile. But I am having a hard time accessing the database information for each user from the views file. I believe I have to pass the user's ID to the controller to retrieve the data but I am not sure. How can I go about this?