Definite integral

Hi, I am working on boundary conditions and I cannot figure out how do I specify the expression ie, definite integral with upper and lower limits.
In the Comsol documentation I read that this can be done using integration coupling variable (that integrates an expression over selected geometric entities). So in the model builder I right-click Definitions and then choose via Model Couplings, Integration. In the settings window I can then give the integration operator a name) and I select the source. So can anyone tell me where to specify the expression and integration limits?
Thanks