While I am not familiar with that particular model, I do have some experience on front load washers.
You are not very specific on where the unit is leaking, front, back, or underneath.
If it is not something obvious, like the flex hoses, the first thing I would check is the door seal/diaphragm. This seals the front of the wash drum to the front of the machine and also seals to the door. This is a common area these machines leak. Sometimes its as simple as lint buildup on the glass door or seal area. Sometimes the diaphragm or bellows part of the seal can get punctured by a foreign object like a pen or screw left in a pocket.
If this proves not to be the problem, removal of the panel and closer inspection should reveal the problem. There are internal tubes and hoses that go from the fill valve to the drum and from the drum to the drain pump and from the drain pump out of the machine.
You can look at diagrams and order parts from Sears. Here are the diagrams for your model.
http://www.searspartsdirect.com/model-number/wfj1254xaa0000/1482/0153200.html