If you want to launch an Assessment for a new Senior, you first have to create her Profile in SeniorGrowth (read this article, How do I create a Senior profile?).
Once you have created a new Senior profile and after you click on the Create New Senior button, you will be taken to the Senior Dashboard page, that looks like the one below:
The Pending Evaluation message in the middle panel means that there is an Evaluation that needs to be completed (in this case, started). The Evaluation is already open in the Right panel, so you just have to start answering the questions (see article about Answering the Questions) by clicking on the buttons underneath the Questions.
If you created the Senior using a mobile application, you will be first taken to the Senior Dashboard and you will have to click on the "Pending Evaluation" link to start the evaluation.
To add a new evaluation to a Senior's profile, click on the "+ Add New" button in the Evaluations panel and start answering the questions (see article about Answering the Questions) by clicking on the buttons underneath the Questions.
Before creating a new evaluation for a Senior, you need to complete or delete any pending evaluation for that Senior.