+1 to craig. if you don't have clamps, here's the Dan Erlewine method: (you DO get to use a hammer, but for pressing, not hitting

)
First things first, work out which frets are loose, no point in doing this to a fret that doesn't need it! You may need to repeat this process to
both ends of the same fret.
Get your hammer, some water thin superglue and plenty of tissue paper all ready to go before you start.
Have the bass held on its side, with the loose fret ends pointing up. You'll want both hands free, so either find some way of holding it upright, or get a friend to hold it for you!
Work one fret at a time, so have one fret completely finished before you move onto the next.
Looking down at the side of the guitar, put a drop of superglue into the gap between the fret and the board. Let it run into the slot for a second or two.
Lay the bass on it's back now and use the tissue paper to wipe up any superglue that has escaped.
Then use the hammer to press the fret down as hard as you can. Don't hit, just press nice and hard.
Hold the hammer in position for about 40 seconds to let the glue cure completely.
Pick the bass up onto it's side again.
Repeat until you've done all the frets that are loose!