Programming with C++ using phpMyAdmin + sale function

I am struggling with the continuation of my project.

I am programming a store console application which lets me put products into phpMyAdmin, but also functions as a cash register. Where I am able to retrieve all the products from the stock and show them in a list, whereafter the cashier can enter the product ID's and ammounts of the products and make 'ticket'.

Now I am able to print out all the products succesfull by retrieving them from the table 'stock' and print them with their id's and names.

But how do I continue now?

Do I make a loop where i ask the cashier to enter the product id + amount ? Do i need to need a new vector? Do i need to use an array? What's the best thing to do in order to continue with this sale function?

Thank you

This is my code: which prints out all the products from the table (works flawless)

   void menuKassa::newSale()
    {
        bool continue = true;
        while (continue)
        {
            cout << "* * * * * *  N E W S A L E * * * * ** * \n";
            cout << "What articles did the client pick?" << endl;
            string products = productlist();
        }
    }

    string menuKassa::productlist()
    {

        int choice;
        vector<Product*> products= ProductDAO::getAll();

        vector<string>productnames;
        bool validChoice;

        validChoice = false;
        int k = 0;
        cout << "What did the client pick?" << endl;


        for (int i = 1; i<products.size(); i++)
        {

            bool a = true;
            for (int j = 0; j<productnames.size(); j++)
            {
                string x = products.at(i)->getProd_Name();
                string y = productnames.at(j);
                if (x == y)
                    a = false;
            }
            if (a == true){
                k++;
                cout << " " << products.at(i)->getProd_ID() << " - " << products.at(i)->getProd_Name() << endl;
                productnames.push_back(products.at(i)->getProd_Naam());
            }



        }
    /*
        cout << "Product ID: ";
        cin >> choice;
    */

    }