See the RAMCO community for detailed video instructions.
Here we will provide a very basic overview of how to accomplish this on your system.
1. Navigate to Settings --> Solutions. Open the RAMCOSubscriber Solution
2. In the left side menu click on the arrow beside entities to view all entities available to you. If the entity for which you want to add the field does not exist, you will need to add it through the "Add Existing" button
3. Select the arrow next to the Entity you wish to Customize and then click Fields.
It may take a few moments for the field list to load. Once it does you can click New at the top of the list to create a new field.
4. Give your field a Display Name and then click anywhere else on the form to automatically fill in the Name field.
5. Leave the Requirement Level as Optional and Auditing as Enabled as the Defaults.
6. Select the Type of Field
For more information on the types of fields this blog post from Dynamics 365 Community gives a good description of each. https://community.dynamics.com/crm/b/crmtipsfromadeveloper/archive/2018/02/12/d365-crm-understanding-field-types-and-their-data-types
7. In most cases you can leave the remaining fields to their defaulted positions.
8. Click Save & Close
9. Click Publish All Customizations
