User sale manager
Go to Accounts > Purchase
Input the wished quantity into one of sale type then click onto the green icon or the button Add all into cart. You've successfully put into awaiting a purchase, you are now redirecting to a new page that represents your cart.
In this cart, you can view a summary of all awaiting purchases with their accounting movements. Click onto the green icon to confirm and validate a purchase. Be sure that you want to validate it because it won't be possible to cancel. The red icon allows you to remove an awaiting purchase. If you want to validate or cancel all awaiting purchases on the current page, you can click on button Validate all purchases or Remove all from cart.