I tried to install the VaultClipse plugin for Eclipse, but all my efforts went in vain.
I then was told by Adobe support that this plugin is old and will not work. They recommended me to use AEM Dev Tools Plugin under Eclipse for syncing source code related to Maven Archetypes (for Java Classes and Bundles), and for all the other source code (Sites, Adaptive Forms, and Client Libs...etc...), we can use AEM Brackets Editor with the AEM Plugin to sync the needed CRX DE nodes. It is not so perfect, but at least there is a way to manage your AEM code in GIT or SVN Repository.
If you have to use Vault, then your only option is to use the command-line interface. If you manage to work with the VaultClipse plugin, please let me know how you resolved the problem.