Imapsync is a (PERL?) script you download, and then run it passing parameters.
If you need OAuth, and it seems so since you want to sync a Google account, you have to download some more files that help you obtain an access token for Gmail.
But as far as I remember, there are no config files needed to run it. Infact I am cron running it every 5 minutes to one way sync an IMAP account to Office365 (needs an OAuth token too, and a second script to refresh the token every hour)
Feel free to ask for more, but I cannot guarantee a timely response.
You can remap IMAP source folder to destination folder. It’s very likely that sent folder needs to be remapped between different hosts. I suggest you to use the dry-run option and examine the log to see if the folders are correctly mapped.
More in detail, I created an user just to run imapsync as a good practice in Linux. Then downloaded imapsync in a subfolder of the user home directory, created two very simple scripts, one with the imapsync command with all the parameters I needed and one for the token. Lastly, using crontab -e, I added two entry one for each script.
You don’t need to put imapsync into etc, it is not a binary and, as far as I know, there is no package that you can install with a package manager, it’s just a script that you download and execute. Anyway, where you put that, its up to you.