hello my brother collects the tyranids and needs help using them to his advantage when battleing can someone please tell me what he should do with each model in his codex to use them fully because at the moment he fails at using them tacticly thank you

Basically - http://1d4chan.org/wiki/Warhammer_40,00 ... s/Tyranids

Then if your buying to play for this codex, this week as best you can you just buy tervigons (big things make small hings have small psychic power) minimum Termagants to make the tervigons troops, doom of malanti in pod, then some hive guard (/missile launchers) some flyrant (flying hive tyrants), choosing horde or a few big things is subject to lots of arguing though.
basic tactic run at it and stab it.

Going to need more information.
What stuff does your brother already own, and what sort of games does he play? By that I mean does he intend to play in cut throat tournaments, go to lgs to play pick up games or just play you at home?