Sonicrida

Could somebody explain to me how to time stretch properly in fl studio? I'm new to this and I've tried a ton of different methods. All I'm trying to do is matchup a song with a simple beat that I've made. My project tempo is 128 bpm and I'm not entirely sure what the bpm of the song is. I've tried auto detecting the bpm and entering a bpm range or trying to turn the time stretch knob until it matches up but I just can't quite get it perfectly. What is the usual way to do this kind of thing? If it helps I can take a screenshot or upload what it sounds like right now.

Hello OC Remix! I'm Sonicrida and decided to join on the advice of Benjamin Briggs and beatdrop after talking to them at magfest 12! I've been the occasional lurker here throughout the years and have loved video game music for basically my entire life. Going to the video game dj battle pushed me to actually learn to make the music that I love so much. My musical history isn't too large. I played piano/violin/drums/guitar at various points in highschool. Later on, I picked up a midi keyboard but it became a thing that I played around with without using too much. And now here I am starting to learn FL Studio. I expect this to be a fun journey!