portfolio

Quote;
can I specify a link to the artstation website on my portfolio on my page ?

Only within the description of your items.
If you post an outgoing link - no matter if do-follow or don´t-follow - within your profile,Julius and co. will come after you! don´t do that.

Artstation is also a marketplace where people sells their stuff. Better contact cgtrader support and ask them if posting external links in your product's description is ok, or if it will get you in trouble.