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.

Wolfgang R. Dick , thanks for your reply.

@Wolfgang R. Dick, will those procedures retain the existing "reads"? Or will they6 be lost and reads start again at zero?

"Reads" will be lost only when you delete the bibliographic entry completely. Deleting only the file will not affect the stats.

Many thanks!