How to do it wrong, way 1
Using the OwnCloud client that is in the Software Sources provided in Linux Mint is wrong! This downloads an older version of the Desktop Client that will fail when connecting to your updated server. You will get an error message like this:
Error: Wrong Crendentials
How to do it wrong, way 2
Add the newer software repository from the owncloud.org website. You are running Linux Mint 17.3 and that is close to Ubuntu and you have the latest Mint OS so you go with 15.10. Wrong! Here is your error message
$ ~ # apt-get install owncloud-client
Reading package lists... Done
Building dependency tree
Reading state information... Done
Some packages could not be installed. This may mean that you have
requested an impossible situation or if you are using the unstable
distribution that some required packages have not yet been created
or been moved out of Incoming.
The following information may help to resolve the situation:
The following packages have unmet dependencies:
owncloud-client : Depends: libowncloudsync0 (= 2.1.1-1.1) but it is not going to be installed
Depends: libstdc++6 (>= 5.2) but 4.8.4-2ubuntu1~14.04.1 is to be installed
Depends: owncloud-client-l10n but it is not going to be installed
E: Unable to correct problems, you have held broken packages.
How to do it Right
You need to add the 14.04 Ubuntu software repository from the OwnCloud download site. If you already added the 15.10 repository and are finding yourself here, then go to Software Sources > Additional Repositories > Opensuse > Edit URL. Change the URL from 15.10 to 14.04. Then do sudo apt-get install owncloud-client and the download will be successful.
Man and Keyboard 