Each customer (company) account with us can have multiple users, as each customer (company) with us has a customer number this can be used to link users to a company. Each user will have their unique log in. When applying it can be decided which users require different access (price, stock and place orders or price and stock only). The users will be linked using the customer numbers so shipping and invoice addresses are available at checkout.
As an existing customer you can apply for an account here.