Just bought a static IP and need help configuring it

I have been using a dynamic IP in conjunction with dyndns.org for a few months now and had that set up fine but due to the computer which hosted the IP software updater sporadically connecting to various networks it wasn’t the best solution.

I bought a static IP address hoping this would solve my problems but I’m confused as to how to set it up.

I have the IP and the subnet mask which I recieved from BT after purchasing the staic IP over the phone.

My main point of confusion is whether I enter the details on the,

1 ) Broadband Link > Advanced Settings > Broadband IP

2 ) Broadband Link > Advanced Settings > Broadband Connection (Do I change PPPoA to Direct IP?)

3 ) Local Network > Advanced Settings > Public Routed Subinterface

I tried doing it the third way but it said my settings were invalid (possibly I have to change the settings above under Private Network?)

I’m perplexed and would apreiciate some help.

PS I don’t have easy acess to the email with the IP details as it is my bosses email account.