If Class Mappings are defined the plugin will create correct IFC element types for each part based on mappings. Select Use Class Mappings checkbox in the Options group and go on by pressing Export to IFC button.
You can create new Class Mappings with New Mappings toolbar button. The plugin will ask you to save current settings and creates a new datagridview that contains all the parts in the assembly and you can go on by selecting correct IFC element type for each of them.
You can edit an existing Mapping definition by selecting it in the DataGridView and then pressing Edit Definition button
After that select correct IFC element type and optionally color for the selected part.
You can remove an existing Mapping definition by selecting it in the DataGridView and then pressing Remove Definition button
You can save current Class Mappings with Save Mappings XML button and open saved Class Mapping definitions with Read Mappings XML button