Before starting to use JChem for SharePoint, its specific features should be activated. You can read about this more in details in the Admin Guide's Activating JChem Features in Site Collections topic. If you have further questions, please contact your system administrator. After this JChem features should be enabled in SharePoint lists, libraries, discussion boards, blogs and wikis (see in Admin Guide - Enabling JChem Features.)
Site settings page can be opened as the below screenshot shows:
On the Site Settings page, click the Site collection features link.
This option requires Site Collection Administration permission. If you don't see the appropriate links, contact you system administrator.
You can activate the ChemAxon features what you would like use. Activate the ChemAxon - JChem Core Functionality feature first, because the others depend on it. After it is started you can choose freely which one to continue with.