Query Needing Sum Function/group By?

select bicycle_shop.bicycle_shop_id, bicycle_shop.company_name, order_.unit_price
from order_ inner join bicycle_shop on order_.order_serial_number = bicycle_shop.order_serial_number
order by order_.unit_price DESC;

this query will bring up a few records for each shop, of the one or more bikes they bought and each bike's price, how do i have these come out to a sum(of the price), so that each bike shop will have a sum of revenue. someone told me i need to use group by and the sum function but i dont know how