If the field you are mapping to is not viewable* from the Lead or Contact picklist, you will need to update Field-Level security for the field in Salesforce.
*If the field type is a Lookup, we are unable to write to this field type and it will not appear
To do this:
1. In Salesforce Setup Navigate to the Lead/Contact Object
2. Choose the missing field from the dropdown list on the object > Fields & Relationships
3. At the top, choose Set Field-Level Security
4. Make sure the field is set to Visible for the correct Profile (if set to Read-Only, then it will be Visible by Default)
5. Refresh Salesforce Fields to see the field in Chili Piper here