For Microsoft Dynamics 2013, we can proceed with the customizations from the following tab
Settings > Customizations
The customization option will give the following detailed page for CRM Customizations.
Solutions exist so that a set of customizations can be purchased, shared or otherwise transported from one organization to another. You can get solutions in the Microsoft Dynamics Marketplace or from an independent software vendor (ISV). A CRM solution is a file that you can import to apply a set of customizations.
Every solution has a Publisher. The default solution has a publisher named “Default Publisher for <your organization name>”.
Solution publisher: The publisher record contains a Prefix value. The default value of this prefix is “new”. When you create new solution components this prefix will be appended to the name. This is a quick way that allows people to understand what solution the components are part of.
Before you start customizing the system we recommend that you change the Prefix value for the default publisher to something that identifies your company.
Links provided for the customizations. Microsoft Links.
It also provides REST and SOAP services links in CRM as follows
Link to the developer Center opens the following official Developer Center of CRM from Microsoft.