Hi James,
In future please make your post subject a bit more specific so its easier for others to search on.
In the left bar, you should see a Plugins option.
It sounds as though it is not there.
There are a few possible causes:
- the wordpress account you are using may not have admin permissions
- there may be custom code, active within the site, which specifically hides this.
I suspect it's #1 though.
If you are unfamiliar with wp, I'd suggest you find a way to get in contact with the original developer (or someone who can debug this for you). There's probably a reason this set of functionality has been disabled ( it may not be a good reason).