You can load an XML document into an XMLType, then query it, e.g.:
DECLARE
x XMLType := XMLType(
'<?xml version="1.0" ?>
<person>
<row>
<name>Tom</name>
<Address>
<State>California</State>
<City>Los angeles</City>
</Address>
</row>
<row>
<name>Jim</name>
<Address>
<State>California</State>
<City>Los angeles</City>
</Address>
</row>
</person>');
BEGIN
FOR r IN (
SELECT ExtractValue(Value(p),'/row/name/text()') as name
,ExtractValue(Value(p),'/row/Address/State/text()') as state
,ExtractValue(Value(p),'/row/Address/City/text()') as city
FROM TABLE(XMLSequence(Extract(x,'/person/row'))) p
) LOOP
-- do whatever you want with r.name, r.state, r.city
END LOOP;
END;