WHY AM RECEIVING THIS WARNING PLEASE? NO ONE ELSE here has access to libre office but me, only one of my devices holds the app.THANKS, L
Either another instance of LibreOffice is accessing your personal settings or your personal settings are locked.
Simultaneous access can lead to inconsistencies in your personal settings. Before continuing, you should make sure user ‘Linzi’ closes LibreOffice on host ‘Linzis-MacBook-Pro.local’.
Do you really want to continue?
LibreOffice has apparently closed unexpectedly and has left a lock file around from when it was last used.
You can simply choose Yes to continue; or if you wish to delete the lock file it is named .lock and should be found in ~/Library/Application Support/LibreOffice/4/ - assuming you are using LO 4 or later. You may have to enable viewing of hidden files in your file manager.
If this answer helped you, please accept it by clicking the check mark 
to the left and, karma permitting, upvote it. If this resolves your problem, close the question, that will help other people with the same question.
The path given is valid for MacOS X but OP didn’t mention his OS. Check path prefix with Tools>Options, LibreOffice>Paths. For instance, under Linux, the directory to look for is ~/.config/libreoffice/4/. Note the difference in case.
I made the assumption of OS based on the warning message mentioned - on host 'Linzis-MacBook-Pro.local'.
Got it, but I added a general tip to give the answer a more universal extent. The remark was also aimed at newcomers so that they mention the bare minimal technical information, OS & LO versions, however irrelevant or obvious it may seem to them.