8GB is ok for 1080p editing, if you're doing anything higher you will need a lot more ram. Back on topic, depending upon what type of work you're doing should dictate any hardware upgrades you need. If you're not experiencing any large slow downs then you probably don't need to upgrade at all. For generall purpose workflows 8GB of ram is plenty. If you do decide to upgrade ram you'll need to make sure your system can support more (most modern laptops can).
The other item you'll need to check is the current memory slot count and what your current memory configuration is. A lot of laptops will come with 2 memory slots; however, manufacturers tend to install 2 smaller memory sticks rather than 1 larger module. It's likely you have...