This temporary Starter account, Explorer, was automatically created for you.
A Starter account can do almost everything a normal account can do such as Liking and Favoriting photos, but it will expire after a while.
To rename this account and keep it for yourself just enter your email address in the header dropdown above.
It's that easy.
I just stumbled upon 500px, what a find. Looking forward share pictures here. Just getting used to all the features of the sites.