Jobs and Accounts can be selected on Sales Order details, and will be posted to job details when the GL account used is either a sales or cost of goods account. Sales Details with inventory accounts will be ignored with respect to jobs.
One way to select a job and account for a sales order is to open the Job tab and do so here. After the selection, each detail line of the sales order will be populated with the selected job and account.
You can also select a job and account for each detail line of the sales order without visiting the Job tab, which is typical when many jobs will be referenced on this sales order. If there is a job/account set for a non expense detail line, then it will be ignored for the information posted to Job Costing.
When the invoice is posted, the sales amounts updates the job/account Actual income, and the cost of goods amounts updates the job/account Actual expenses.