If a mortgage is applicable to your client’s purchase you can upload a copy of the mortgage offer under the Conveyancing tab by clicking 'Start' next to the 'Mortgage' step. This is just for reference and to notify the other stakeholders in the process that the mortgage is progressing.
Don’t worry, no one other than you and your client will be able to see the mortgage details, the others will just get a notification to say the offer has been received. Once all conditions to the mortgage have been settled, use the ‘confirm’ button to notify all stakeholders. Alternatively, you can simply click 'Mark completed' next to this section if all of the mortgage steps have been completed offline.