How do I assign more than one contact to an opportunity

How do I assign more than one contact to an opportunity

Ive been using the free version now for a few weeks to evaluate whether this is right for my small company as we are not yet wanting to spend a lot on CRM
My company is linked to the construction industry providing high rise glazed structures and as such we will receive enquirers/tenders (opportunities) for a new office block, for example, from more than one large contractor who will all be tendering for the actual building construction work.
I cannot see how i assign more than one Company to an individual Opportunity!

At present i am assigning one of the companies related to an opportunity in full but having to put the contact name/tel no/email ONLY of any others under "Contact Roles"

Am i missing something or is this a shortcoming of this software which is more aimed at the "hoover" salesman?

Can anyone help?