your hbs can't tell you what it is?? i'd ask them again.
how dark is it? i think all grain darker than pale will have some steeping qualities. (stand corrected if not so). but some pale grains also steep eg cara amber or carapils.
what does it smell like eg delicious sweet, slightly dry, no strong smell in any direction, slightly acrid?? that will steer you into the grain category. and if it smells like stale flour, i'd ditch, cos that will go through your beer. but if it smells stale first up, have a 2nd smell a few minutes after you've taken the lid off. sometimes that is just trapped stale air, and with a bit of fresh air, the grain will smell rosy again.
they need to be stored in a dry cool place, fridge is not always dry. in a dark cupboard would be better.
i assume they've been milled. if they are, i'd use them straight up as a steeping grain, whether crystal or not. the reason i say that is that milled grain has a short life, and one way or another, it will get you into steeping grains. if they're not steeping grains, they won't ruin your beer. if they are, then you'll lift your kit big time.
oh - just saw the 'lager' bit. if it's lager grains, probably either pils or a pale ale malt, and both need mashing. i'd suggest a steeping mash (no such thing technically).
that means steeping it for an hour at as close to 63-68C as you can keep it. it should in any event lift the flavour a lot.
if you do that, remember to boil it for another hour, partly to knock out the nasties and partly for flavour improvement.
so yeah - steep (mash) for an hour
drain fluid (wort)
pour 72C ish water through grain to flush more goodies out and add to drained wort.
boil all drained wort for an hour.
add to kit.
