At first you need to know how much BPM the vocal sample has and need to speed up or slow down it to the BPM of your track.
Rightclick the 'time' knob and choose 'type in BPM' and type the BPM of the vocal sample in it.
Then choose 'Pro transient' in the dropdown menu right from the 'time' knob. This will normalize the sample, so it will not listen like its up or downpitched.
Now you need to put the sample on your track and fit it in the beat, I am just listening carefully to it.
Many vocal samples have a short beat before the vocals start, so it easier to fit them in the track.
One additional point: make sure the original vox recording/sample is on point in terms of quality. You can only enhance/fix it so much through compression, EQing, etc., the better it is in terms of original source quality the better the end result.