I think they are looking for someone in Uruguay who would accept the financial burden of your visit in terms of housing, food, medical insurance etc. in the event you did not have sufficient income.
I would contact the closest Uruguayan Embassy and ask them for advice on how to do this.
Also, maybe there is someone from your country already here. Have you joined the Facebook group?
What kind of work would you do here? Maybe there is someone in the same field who could suggest something. Do you belong to any groups, volunteer organizations or church that might be here too. Perhaps they would help. Maybe you could come as a volunteer for an organization that does charitable work here. If you search for volunteer in Uruguay you will see some ideas by different groups and also people looking for volunteers to help with projects.
Hope this helps!