How is the numeric value obtained through Diffie-Hellman key exchange used?

Question

I'm trying to implement the TLS handshake for specific cypher suits with Java

so I chose simple DH as a key-exchange algorithm

I have successfully completed the key exchange algorithm, and I don't understand how this number is actually used.

I chose random prime number and DH secret key with a size of 1024 bits, and the generated numeric value of the symmetric key is as follows

137788568906486456562313443251433625845738808626213687842428636488613021697893174760087427050476313862114101648826514308630193757158023355782732286841194048890730724983728673832483012519924831013247552765933483415273172062507912219558443488454534677453627247897385118516061200838456501806287350964669621095063

I think this is the pre-master-secret, how do I use this value?