There are two ways to do this:
1. Click on a job position and under the Sourcing tab, select Inactive Job Boards. Here you can select the desired job boards by checking them under the Activate column and clicking Update. If you had selected Paid Job Boards, you will be taken through a payment wizard to complete payment.
2. Go to Jobs > Management. Select the desired job positions to post by checking them. From the Group Actions drop down above, select Post to Job Boards. This will take you through a wizard, where you can select the job boards, complete any payment, and post the jobs