From your 'My Hub' page (please see below)
On the left hand side of your account, you will see the side menu in which you can select 'Contacts'.
You then select the client profile
You can then click 'Progress Photo's' from the list under that client's profile picture
where you will have the option to 'Upload Progress Photo'.
Simply click the upload file icon
Select the pics and click the 'Upload' button.