As per the documentation XPP cannot interpret text or file entities and one needs to use a transformation tool to convert the text entity before importing the instance into the XPP division. Which transformation tool can be used for achieving such a conversion ?
There are a number of possible transformation tools that are part of XPP that you could use.
I suggest you read Chapter 3 of the latest version of the XPP Transforming Data manual.
Here's a part of the beginning of that chapter (text in brackets added here by me):
With XyChange, you can transform text to a format appropriate for your needs. You can also choose the tool appropriate for your task. XyChange can be used to launch Perl or OmniMark scripts, or XSLT style sheets. Each transformation technology has its strengths and weaknesses: