A Records

[#1]

Hiya,
I have a domain with plusnet and my hosting at a 3rd party. I need to direct traffic to domainname.co.uk and www.domainname.co.uk to the new IP address.
I'm OK with the www. one as I just setup an a record called www and point it to where it needs to go. However, what do I do about the one without the preceeding www.?
Thanks

[#2]

Setup another A record:

domainname.co.uk.          A          <ip_addr>

Note the trailing dot on the left hand side.

[#3]

OK thanks.
Can I use CNAME in one of the records, as I think what I did before was to have domainname.co.uk. as A record with IP address then www as CNAME pointing to domainname.co.uk. but it didn't work?