To navigate to the Settings page, navigate to your User Name in the top right hand corner of the screen, then select the drop down arrow next to your User Name, select User Profile from the drop down menu.
Next click on the little camera icon next to the Avatar thumbnail.
Next you want to decide if you want to create a custom Avatar or upload a Picture.
If want to upload a picture you can Drag and Drop the image file into the upload box or hit the Browse button and manually select the image file you want to upload.
If you want to create an Avatar select the Avatar button.
Next, browse through the different options and select the ones you prefer. You can see the different options appear in real time on your Avatar.
Once you're happy with your choices, select the Submit button at the bottom.
And now you have your brand new Avatar that everyone can see!