You should make sure that the Reflection library is checked in the pane/tab at the far right side of the IDE. If you are using B4A 2.0 or above, the reflection library should be updated to version 2.2.
You need to make sure you place the .xml and the .jar files in the XtraLibs folder. This is a folder you must setup if you have not already done so. Then be sure your IDE is pointed to this directory for your Additional files. In the IDE, click Tools, then Configure Paths, then you will see your Additional Libraries field. Browse to were you placed these files and that's it.