I find it helps to lower your feed dogs first, that gives you just a tiny bit more room. Put the walking foot in your right hand, put the lever over the needle thingy (technical term) first, and angle the foot into the right place until clipped on the cone.
You may be worrying about where the needle goes because the original feet had a bar going in front of the needle, then more recently, they came with two different bases, one with the bar, and one without, that you could interchange with one another. Perhaps the one you have is the 'open' one.