Go to your profile dashboard, and click "edit profile". At the bottom, click the profile picture button, and a file picker will pop up so you can select your new profile picture.
Click "Post Ad" at the top right of your screen, and follow the next three steps to add information about your item. Please note, anything with a red asterisk is required information, and you cannot move on to the next step until those items are filled out.
You can see notifications of new emails in the top right, as well as how many messages you have. To view all of your emails, please go to dashboard > messages