Q: Updating from 10.5.8

Hello

I am struggling to work out how or if I can update the OX of my Mac which is not that old.  I have seen previous questions about the same problems but the answers give so much information I still cant work it out.  I have beneath supplied the details from by Mac from system profiler.

Model name Imac

Model identifier iMac8,1

Processor name Intel Core 2 Duo

Processor speed 2.4 GHz

Number of processors 1

Total number of cores 2

L2 Cache     6MB

Memory 1GB

Bus speed 1.07GHz

Boot Rom Version 1M81.00C1.B00

SMC Version (System) 1.29f1

One further question how do I find the year of manufacture of my Mac.

The reason I am trying to update is Firefox and Chrome tell me that they no longer support 10.5.8

Any help appreciated but please keep your answer fairly simple as Im nearly a old fart now and all the tech stuff flies strainght over my head.

Mike