For index queries, you put the index name in the index name field, there is some suggest thingie there to give you the right name.
Then you will have a new text box, where you can type the lucene query on the index
Something like:
Name:Ayende
for linq query, you write the full bore linq query, and then execute it.
Something like:
from doc in docs
where doc.Name == "Ayende"
select doc