Download and untar source files

lame is not available through a yum repository; but it can be obtained and installed from Dag Wieers' RPM repository
rpm -ivh

You may wish to check that the link specified here is actually the latest and greatest. Look at the files available on Source Forge and pick the latest one there.
cd /usr/src

Get the latest released version of zaptel
tar zxvf zaptel-1.4.x.tar.gz 

Get the latest released version of Asterisk
tar zxvf asterisk-1.4.x.tar.gz

tar zxvf asterisk-addons-1.4.x.tar.gz