Hi Duong,
You need to link your attributes to a list of entities by passing in a datasource property
<property key="data" type="datasource" isList="true" required="false">
<caption>Data source</caption>
<description />
</property>
and linking it to the attribute:
https://docs.mendix.com/apidocs-mxsdk/apidocs/pluggable-widgets-property-types/#attribute
You can then retrieve the data from the list using the patterns outlined in the docs: