My question is how to import the xml data, into specific field.
Your question is just too generic. Please post a file with the XML.
The Import Records script step needs two things: the source (of the data) in a format which FileMaker can 'digest' and the database table into which the data will be imported. Yes, you can import and create the table/fields the first time you import. However if you have a database already, then you need to provide a "mapping" for the data (from the source to the table). Keep in mind that ONLY ONE TABLE/LAYOUT is used at a time for import. If your source has "related data", you must create multiple imports to get it all.
There are various ways to "read" the XML and push into fields (plug-in, custom functions, XSLT - to transform to the mapping needed, etc.) How comfortable are you with any of these terms (what level of experience to you have with any of them)? We will help you step through this, but need a bit more information from you, please! What version of FileMaker are you using?
Retrieving data ...