In Conformal Channel tab, under channel properties in the 'Obj.' row select your mesh object from drop down menu . And then click 'Create Channel'

If irregular channel got generated, check 'cen_end1(Z-)' and 'cen_end2(Z+)' values such that 'CentralCurve' lies completely inside the Mesh object you selected in the 'Obj' under 'Channel Properties'. By default central curve is generated with 0.1 and 0.9 values with respect to the object bounding box.