Guys:
I have two 32 bit apps (to control functions on a ham radio) that I installed on a Ubuntu 12.04 LTS 64 bit. The apps apparently install, but they don't work. I checked that my apps were functional by running them on a 32 bit Ubuntu machine, where they work fine. What I need to do to have these two apps work on a 64 bit machine? Thanks.

Properly designed 32-bit apps should be runnable as long as any needed 32-bit libraries are installed. Please add the actual error that you get. Check for log files created by the app and also do

You need some 32-bit .so files installed into some lib32 directories (such as /lib32 or /usr/lib32).

First you need to figure out which .so files you need. If those apps are launched by directly invoking 32-bit programs (rather than indirectly through scripts) it is easy to identify the missing .so files using the ldd command.

will tell you all the .so files and which were found and which were missing.

Next go to the web site http://packages.ubuntu.com/
and scroll down to Search the contents of packages and type the name of a missing .so file in the box below that and search.

If you are lucky, one of the packages you find it in will be a compatibility package (a package of 32-bit .so files designed for use on a 64-bit system). In that case, you can simply install that compatibility package.

Otherwise, you might find the 32-bit .so file only in a 32-bit package. In that case, there may be some better way (such as a chroot to fool the package installer), but the only way I know is to download but not install the package, then open the package file with an archive program instead of a package installer and manually copy the .so files to where you need them. If the package says the .so goes in /lib, you need it in /lib32. If it says /usr/lib, you need to in /usr/lib32. Similar rule for less common places.

If you install .so files manually from a 32-bit package (rather than automatically from a compatibility package) you also need to use ldd on each of those .so files to see if they need other ones that you must find and install.

The basic compatibility package that all the others depend on is this one:
http://packages.ubuntu.com/precise/libc6-i386
So if you don't already have that installed, install it before you even start investigating what you need. It is possible that is all you need. But anyway you do need it, and having it there to start will reduce the time it takes to find out what else you need.

You should also check and make sure the package multiarch-support is installed.

That is the package name in the Debian Wheezy repo. It is possible that this is different in the Ubuntu repo.

This is probably needed in your install of some packages. 12.04 is based on Wheezy.