The first step before you start playing with PASM code is to get a copy of the source code and compile it. There is some information on this in Section 22.214.171.124. For more information and updates, see http://www.parrotcode.org and the documentation in the distributed code.
The basic steps are: 
$ perl Configure.pl $ make $ make test
With versions of Parrot later than 0.0.10, you can speed up the testing process significantly by compiling IMCC first (see Section 7.1) and running the tests with IMCC instead of the Parrot assembler:
$ make test IMCC=languages/imcc/imcc
Once you've compiled Parrot, create a small test file in the main parrot directory. We'll call it fjord.pasm .
print "He's pining for the fjords.\n" end
.pasm is the standard extension for Parrot assembly language source files. Compile it to bytecode, using assemble.pl :
$ ./assemble.pl fjord.pasm --output fjord.pbc
You specify the name of the output bytecode file with the --output (or -o ) switch. .pbc is the standard extension for Parrot bytecode. Finally, run the compiled bytecode file through the parrot interpreter:
$ ./parrot fjord.pbc
That's all there is to it. 
If you're anything like me, the next thing you're going to do is symlink parrot from a directory in your PATH , and write a tiny script for the assembler so that from any directory you can just type:
$ assemble fjord.pasm $ parrot fjord.pbc
These last steps are optional. In fact, something similar may be done for you with a make install target by the time you read this.