Thank you both for helping me. I just wanted to know if the folliwing two words are correct:"them" and "alerts".

Question

1) Go through security and show your passport.Put your hand luggage and any metal object in a basket for them (?) to be scanned.
2) Then walk through the metal detector. If it alerts (?), a security officer will check your body for metal.

Answer 1

Here's how I'd write them. Remember I'm in the US! Dr Russ is in the UK, so his terminology might be better for you.

1) Go through security, and show your passport. Put your hand luggage and any metal objects in a basket to be scanned.

2) Then walk through the metal detector. If it goes off, a security officer will check your body for metal.