To make changes or additions to your account - such as adding a Profile Picture, changing your Name, changing your Username, or even adding information to your Bio - simply press your Profile Picture found in the top-right corner of the main Community Homepage. This will take you to your profile: from there, select the More menu (...), and 'Edit Profile'.
From here, you can easily make changes to the details of your account. Please note, this information is all public, and as such you should consider our Community Guidelines when making any additions or changes.
See the clip below for a step-by-step: