Hello Jaime, if your grandmother's ancestors are already listed on WikiTree then I would definitely advise you to contact the Profile Manager (PM for short ) or managers looking after those profiles. PMs are often ( but not always) related to the people they are working on , so there is a high chance one of them could be a relative of yours - a cousin, of some sort, maybe. Contact them by going to one of the profiles concerned and finding the link to send a private message ( it is just under the "Died XXXX" field) and next to where the profile manager is named.
The basic kinds of proof required are birth, marriage, and death records. Also extremely helpful are baptism records and Census records. Old wills can also help to prove relationships as they were legal documents.
Just to emphasis what Lynda advised - check every step of the way, to make sure that none of the profiles which you are going to add are already on WikiTree. This avoids duplicates and also leads to discovering new relatives and tree branches.