You mean they are overgrown?
It isn't that hard to clip a cats claws - as long as they are co-operative
You'll want the small size dog nail clippers - Pets at home stock them and should still be open if you have one near.
With someone holding kitty, gentle squeeze the paw at the nail base so make the claw come out, then snip off the end. Be careful not to cut the quick (the blood vessles) - if the cat has light coloured claws, you should be easily able to see where this is.
I've only ever had to cut one cat's claws - when RB got old and sick he stopped going outside and didn't scratch his post or the furniture. I cut Layla's claws because she is an indoor cat can't fully retract her claws, so we often get accidental scratches.
I would
never clip an outdoor cat's claws unless
absolutely necessary - they need them for climbing.
If the nail has pierced the pad, you'll need to clean it up after clipping using hibiscrub or salt water.
If you can't clip the nail and it has pierced the pad or the cat is in pain/limping then phone the emergency vet for advice.
If you do clip, but the cat still seems in pain, call the emergency vet for advice.