Could you please elaborate a bit on what is "LOC" and what polygons you got? Are you going to test a specific functionality of the Network Analyst extension (this will define what input data you'd need)?
All right. What you have to do now though is to convert your polygons into centerlines (polylines) which can be used in Network Analyst. Some alternatives you have are as below:
1) Manually digitize the lines from the polygons.
2) Run the Feature Class to Coverage tool (Conversion toolbox > To Coverage) and then run the Collapse Dual Lines to Centerline tool (Coverage toolbox > Data Management > Generalization). Experiment with max and min width of the features here.
3) Convert your polygons to raster (Conversion toolbox > To Raster > Feature to raster) and then run Shrink tool (Spatial Analyst toolbox > Generalization) to obtain a "single-line" raster. Then you can convert the raster back to vector line with the Raster to Polyline (Conversion toolbox > From Raster).
4) Use ET Geowizards from http://www.ian-ko.com/ (tool is called Create Centerlines from Polygons).