If you mean how to update the uploaded file, see https://help.researchgate.net/hc/en-us/articles/14293099743121-How-to-make-content-private-or-remove-it for instructions how to delete the file. After this, upload the new version (see "How do I add a full-text to my publication page?" in https://help.researchgate.net/hc/en-us/articles/14293005132305-How-to-add-research). If you mean how to update the bibliographic information, see "How do I edit my research item's details?" in https://help.researchgate.net/hc/en-us/articles/14293081125777-Reviewing-editing-and-featuring-your-research for instructions.