Explanation

Step 1: Call the login logic.
Step 2: Retrieve the Course credit entity metadata by using RetrieveEntityRequest with EntityFilters = Attributes and LogicalName The RetrieveEntityRequest.EntityFilters property gets or sets a filter to control how much data for the entity is retrieved.
Step 3: Define the AttributeMetaData for each new field.
Step 4: Call the RetrieveAttributeRequest with LogicalName for each new field.
The RetrieveAttributeRequest contains the data that is needed to retrieve attribute metadata.
Reference:
https://docs.microsoft.com/en-us/dotnet/api/microsoft.xrm.sdk.messages.retrieveentityrequest.entityfilters?view=