[ESPResSo] how to set up a charged plate

[gil claudio]

Hi everyone,

How does one set up a plate that is uniformly charged?

For example, I have a box 100 x 100 x 100 with a constraint wall at the bottom 
of the box.  I would like to charge this wall uniformly with, say a total 
charge of +50.  How can this be done?

Thanks.

Gil