Transcription is THE WAY to learn how to improvise. Anyone can do it...maybe your ear isn't as great as your classmates or as the great, Wynton Marsalis. No worries.
Start with any Miles Davis solo...one note at a time....and before long you'll be assimilating jazz language, style, and articulations. From the album, Cookin' with the Miles Davis Quintet, Miles' solo on the track "Blues By Five" is the perfect first transcription. In the first 12 bars or chorus, some simple tasty chromaticism and motivic development are a couple of the key concepts you can assimilate from the solo. Get a spiral notebook to keep all of your transcriptions together in one easy to access place. I suggest that you write out the solo in scale degrees and follow the shape of the solo lines he creates. Like this:
1 1 1 1 1
Once you've gotten scale degrees down, it's time to start changing keys! Don't write them down!. Just have the scale of the new key in front of you if necessary, and see what you can do only looking at the numbers. I'll bet you'll be shocked at how well you can transpose this solo. From there you practice improvising one of your own phrases over the blues and then one of Miles' phrases from the solo. Eventually you won't be able to remember which is your solo ideas and which were Miles'. That's when you'll know you're on the right path to expressing yourself through your instrument.