Compaq CQ58 261SA RAM upgrade advice?!

So I have a Compaq CQ58 261SA which currently has the memory it came with, 4GB. I want to upgrade to 8GB of ram, but want to be sure what the exact type is that I need to buy for my specific laptop. Here is some information on the laptop I have thrown together:

Model: Compaq Cq58 - 261SA
Product number: C6J39EA
Processor: Intel(R) Celeron(R) CPU B830 @ 1.80GHz
Installed memory (RAM): 4.00GB (3.89 GB usable)
System type: 64-bit Operating System, x64-based processor
Graphics: Intel(R) HD...

Compaq CQ58 261SA RAM upgrade advice?!