seeing as almost all modern music today doesn’t have much tempo variation, u can find the first downbeat and set it as ur 1.1.1 (this may be in the middle of a word, on the second word or before the word… pain in the ass), right click on it and select "warp track straight from here". after that, u shouldn’t have to do to much work on manually warping it. in the box where the clip bpm is, type the bpm in there and ur acapella should be pretty much lined up.if u don’t know the bpm just give it ur best guess and us the up and down arrows to make changes till u find the bpm that fits. if its not 100% on point i usually make another warp marker all the way at the end of the clip, zoom in on it and start moving it to the left or right till it falls in sync.( keep in mind that no producer makes there tracks at 128.12 bpms, its gonna be 128 even or whatever bpm ur working with) this has worked for me, also by doing it like this u won’t have the added audio artifacts that putting warp markers in the middle of ur clip can possibly leave. hope this helps out!