Hi Yasmeen – you can do this using the “GIS Tools” menu in the geometry editor:
1) Draw a temporary/dummy boundary condition line in the geometry editor (location doesn’t matter…you just need to have a line somewhere in the model).
2) Click GIS Tools –> 2D Flow Area Boundary Condition Lines
3) Select “Import Lines” and import your .shp file. You can rename it in the same window if you want
4) Delete the temporary BC line you created in step 1
Hope that helps.