You really need to read a bit about it. There's plenty on this site.
Cloning is the one thing where everything needs to be 'right'.
Quick tips include....
Sterility is ket. Bleach and rinse all equipment prior to use.
Cut at 45 degrees below 4th node with sharp, sterile razor blade.
Get STRAIGHT into water to avoid an air-lock in the stem.
Remove bottom leaves and petioles, leaving only 1 or 2 top sets of leaves.
Use root-riot cubes or seedling and cutting compost.
Use a dome or propogator.
Use low light (1-1500 lumens/ ft) or a north facing windowsill.
Use plain, ph'd water for both watering and misting of the leaves twice daily.
Keep humidity at 95-100%.
When rooted, remove the cover for a short period of time daily, slowly increasing the time to acclimatise the rooted cutting.
Watch out for The base of the stem rotting. If it starts to, remove the dome.
Cloning takes practise but it's a skill well worth learning.
Good luck.