Goto your domain registrar (e.g.GoDaddy.com) where you purchase your domain name from, log into account, change the nameservers as follows:
You may have to wait for a few hours to 24 hrs for the setting to propagate to all the DNS servers around the globe. My own experience is about 3-4hours.
No changes require at the Lacehost (Leapswitch) web host (e.g. A(host) and CName settings).
On a side note, I saw a bad review from an irate customer of Leapswitch. My friend has used Leapswitch for several years who in turn recommended Leapswitch to me, I must say that the customer service response and stability of the web hosting (for a non mission-critical website such as BoomzTown) has been very satisfactory so far, in case you have any doubt, do drop me a mail. P.S. I do not work for or in any way related to Leapswitch except as a client of theirs.