I've stored many items into the "Workshop? by hitting B. I can't however figure out how to get those items back without using additional materials.

What am I doing wrong?

I'm trying to figure out what you're saying:

Are you trying to get items out of the Workshop inventory and into your own inventory?

Are trying to use items to build other things by using their parts?

He's talking about when you look at a built object in Build mode, and it gives the "Store in workshop?" option. Once you've stored away that couch/bed/water pump/turret, how does one get it back out?

I've wondered this myself...

Isn't it used automatically when trying to build an object that is already stored? That's how it works for weapon mods.

If you stored let's say a turret when in build mode you should notice a number 1 on the turrets image when you select it showing you have one prebuilt. Unless your building the item in 1 settlement then trying to move it to another you'd need to create a supply line between both settlements for that to work.

Ohhhhhhh now I see what they're saying. Duuhh

Yes, this is how I thought it works and from my experience it does? Midniteryu describes it best

I could see it though that some items might be bugged and it won't work. Have to remember it has to be that specific item. Even though all beds use the same materials and are essentially the same, they are different styles so you can't store one type of bed and be given another. Has to be that bed again. Another possibility would be that some items are bugged. I was doing this last night with the high tech lamps and it works as intended, but I seem to recall my first experience with it is that it didn't always work? Little foggy with it. Need to test some various items and such, but I know there was a reason that I started to scrap items I didn't want instead of storing them. Not all of them, but really the ones I didn't want and would rather have the materials back (even if I lost a couple here or there).

When working properly, if you select to store a crafted item in your workshop inventory, that item in the list ought to update with a count of how many of that item you have in inventory. So if you store 4 wooden foundations, the next time you go to build a wooden foundation and select that item from the building menu, you ought to see a "4" in the thumbnail for that item.

I think part of the problem might be that not all the objects are things you can build. I stored the shelves in the front area of the Red Rocket, but then couldn't find shelves in the same style in the Build->Shelves menu.

Maybe. Not sure.