I am new to Salesforce development. As part of setting up the environment, I have installed the Force.com IDE plugin in Eclipse Neon (4.6.2). After the installation of the plugin, I can create the slaseforce application and deploy the same in server and see the changes. But the content assist or code completion is not working. Someone has suggested to use Apex LS Editor plugin. Its not working after the Apex plugin installation. I also do not see any option under Window-->Preferences.
Please let me know how to fix this.
Note: Location of the Apex plugin