Moving from Dropbox to Google Drive

I have moved all the files I used to have in Dropbox to Google Drive as that gives me more free storage.
However I also use Open Office to view these files which are a mix of spreadsheets/pdfs and Word type files.
I cannot figure out how to "tell"Open Office to look in Google Drive instead of Dropbox.
I still have the files in both cloud storage locations.
Anyone tell me where I am going wrong please ?
I also have a home finance program that I use daily and that defaults to Dropbox as well.
I cannot seem to find a Google Drive app for my iMAC unless I am just being thick again.

Here's one, https://www.google.com/drive/download/

Thanks

Note that the older version of Google Drive will no longer be supported after Dec 11, 2017. The Link above is for the newer "Backup and Sync" by Google. Make sure you read how the new version works before deploying it.

Tried to download Drve but said it was not for my device so got Back up and Sync and that seems to be working ok but I must admit I did not read fully how it works but I wil now read it properly.