how to take of valve springs

You do not have to remove the valve springs in order to remove the cylinder heads!

Once everything else is disconnected from the cylinder head, remove the eight head bolts and then you should be able to lift the cylinder head from the engine.

yes but i want to remove them,so how do i do it?

you'll need a valve spring compressor.

Here how:

1. With the cylinder head(s) off of the vehilce (assuming that you are taking them off - if not there is a way to remove the valve sprigns with the heads on the engine. however then you'll have to prevent them from falling into the cylinder - so I'll describe the process with the heads removed)
2. use a small hammer (preferably a soft faced hammer - but a steel h ammer will do), tap [I said tap] the outer edge of each vlave spring (this loosens them up and reduces the effort you have to put forth using the valve spring compressor)
3. position the valve spring compress so that the round platform is against the valve head and the fingers of the compressor are on top of the valve spring with the top of the valve spring in beteeen the two fingers.
4. push the handle of the compressor in towards the cylinder head, forcing the spring to compress.
5. on each side of the valve stem. now reveiled by the compressing ot the spring, are two valve keepers (small half round steel collars which hold the spring assembly onto the valve stem).
6. remove the two keepers [do not lose them, you'll need them for reassembly.
7. Repeat on all other valves.
8. keep the valves, springs, rotators and shims in the order that they were removed [for proper assembly]