Click on the List Assessments link in the list of tabs at the top of the page to view a list of all the assessments you are involved with. Your assessments will be listed in a table with one row per assessment, as the following screenshot demonstrates:
Change the order of the table by clicking on a column name. You can load an assessment at Stage 1 by clicking on its name. Alternatively the Go to Stage column displays each of the five stages for every assessment as a button. Click on the number to load the relevant stage. Any stages that aren't available are greyed out.