With the SMD/DMX plugin, importing is easy. Note that the import plugin does not fully assign the textures to the mesh. That is described later.
Open Blender
Click File > Import > Source Engine (.smd, .vta, .dmx, .qc) menu item
Select smd file you want
Click Import SMD/VTA, DMX, QC button
Check that the mesh shows.
Select the mesh.
Click the Scene icon (blue background in image) on Properties toolbar (bottom right panel in the image).
Click the triangle beside "Source Engine Export" (toward the bottom right) to open that section, if not already open.
Click on the SMD button. The plugin defaults to DMX, but I am only familiar with SMD format.