However, I feel obligated to tell you that Chopin generally wanted his trills started on the upper note instead of the principal note. Whether you follow that or not is up to you.
First of all, what you are referring to is called a trill. A tremolo is when you rapidly alterate between two nonadjecent notes.
Secondly, the fingering 132 implies that you should strike the note first with the thumb to make an accent on the principal note then switch to trilling between 3 and 2. The 243 serves the same purpose, but I don't think that I'm alone in saying that 34 is the worst trill combination possible (the tendons between those two fingers are bound up and make independence difficult, if not painful). However, I feel obligated to tell you that Chopin generally wanted his trills started on the upper note instead of the principal note. Whether you follow that or not is up to you.
So, in this case I hit F note and start trill again with F ?
No, just start the trill on the F.By the by, the fingering reflects the fact that you are most likely to play the previous high Bb with your 4th finger, with 3 on the Ab & 2 on the G. As kriskickass says, you want to avoied trilling with 3-4, so the suggested fingering is a neat way of working round to a 2-3 smoothly and easily.
If you want to make this trill sound really musical, then you give it a beginning, a middle and an end.You start it more below top speed and accelerate through the first quaver, trill the middle quaver up do speed, then slow the trill on the final quaver, so that the turn fits neatly on the end.I have attached an example. Sorry it isn't my best playing, but I played it without warming up.
BTW, how is it that you're learning Chopin's Ocean etude before learning how to properly play a trill?
Topic: Chopin tremolos (newby question) 