This is private service that needs a subscription. UPM has an agreement to use this resource inside the UPM network (i.e., the computer must have an IP address belonging to the UPM network). But creating an VPN with the UPM, you can also use it from home.
In this document [Link] (in Spanish) you can find a tutorial to create an account from a UPM computer and to use the basic functionalities of RefWorks.
You can also find in this [Link] some update video tutorials (in English) to learn to use RefWorks.