SENT should be in a sentence like this: I SENT my friend a letter.
SCENT is used in a sentence like this: Mmm... The perfume has a sweet SCENT.
If you want to use them in the same sentence:
"
The fan blowing the air sent an enjoyable scentthrough the air"
or
"I sprayed some of the perfume on the paper and sent him a letter with my scent in it"