When viewing a concern click on  Send Alert To... on the right-hand side underneath Actions

This will pop up a box allowing you to select the colleague you would like to alert and send them a message: 

Selecting the staff members field will allow you to select either user groups, or by clicking the + next to a user group, individual staff members within a user group:

If required you can then write a message to inform the users why they are receiving this alert. This message will be displayed in the email that is sent to them.