When you have found a picture (avatar) you want to use,right click your mouse over it and select 'save picture as' then enter a name and destination for the 'picture',destination is where you store it on your pc.
Then when you enter DSC site,go to the 'control panel' then 'edit profile' then scroll down to AVATAR URL and click on browse,this will allow you to search the destination(folder) for the picture.Then 'open' the picture and the box next to the 'browse' button will have an address in it.Then just click 'edit profile' to upload your avatar