extension in sales order header and product level in SAP C4C for Sales

Hi eveyone,

I am facing issue with

1)  creating new column in sales order item level screen.

2) I have created 2 custom fields in sales order header level but i cannot create as ObjectValueSlector box and dropdown box instead i m able to create only display type as inputBox.

3) and can u tell me where should I write 'call to odata service' for fetching data from ECC to my customized data.

Best regards,

Santosh