How do I create indexes?

If you haven't created partitions yet, then create index on parent before calling create_range_partitions() or create_hash_partitions(). The index will be automatically propagated for each partition as new partitions created.

If you want to create index on existing partitions use this snippet (don't forget to change table and key attribute names to actual names):

do
$$
declare
  rec record;
begin
  for rec in select * from pathman_partition_list where parent = 'table_name'::regclass
  loop
    execute format('create index on %s (attr_name)', rec.partition);
  end loop;
end
$$
language plpgsql;