This archive holds 3 files:

readme.txt: this is the file you are just reading.

IC_basic.lps: 
This is a basic IC schematic design library for xcircuit. It is intended as 
a demonstrator how to use xcircuit and how to create a SPICE-netlistable design.

IC_basic_models:
Simple spice models to make the netlist generated by xcircuit simulateable.
These models do not belong to an existing technology. If you want to
customize it for your technology you have to modify the models. (Do not forget
to adjust the names in the library 'IC_basic.lps' if your model file uses
different names.)

Usage:
Simply draw a schematic using xcircuit and the components of the library 
'IC_basic.lps' . Then netlist using the buttons 'Netlist' and 
'Write spice netlist' As a result you should get a netlist (something like
'Page 1.spc').
The file 'Page 1.spc' still lacks the models. These can be attached by
'cat IC_basic_models Page\ 1.spc > spice.in' .

Stimuli:
Depending on your environment you have to add stimuli to the file 'spice.in'
(this applies for instance to Berkley SPICE 2G6) or add them in your 
simulation environment (for instance if you use OPUS).

How SPICE gets invoked depends on your simulation environment. Command line 
probably is the most simple approach:

'spice spice.in > spice.out'

should do the job.
In some environments you may have to source the code typing something like
'source spice.in' . 

Good luck and lot of success,  Ricardo Erckert

P.S. I am not familiar with sim. These calls most likely are buggy!