You can subscribe to layouts from within steam using the "workshop" tab in the community hub.
When you subscribe to a layout, it will download through steam.

After all of your workshop content has been downloaded, simply launch the game as usual.

You can find all downloaded layouts on the main menu (the big "new game" menu) under the "Workshop layouts" option.
From here you can load any downloaded save, and then edit it as you please in the same way as any other save.

You can also find your downloaded saves listed on the pause menu (the menu with graphics, controls, etc) under "workshop" and then "downloaded layouts".

You can upload your saves to the Steam workshop in-game when playing both in VR and on PC.

Simply go to the "workshop" entry on the pause menu (the menu with graphics, control options etc).

From here you can browse downloaded saves and choose to upload your current save (the layout you are currently playing) or update a previously uploaded layout with a newer version.

Choose "Upload current layout" to go to the upload menu.

From here you can set a name and description for your layout.
You can also set the thumbnail to be used in the steam workshop and set the location players will spawn in when they play your layout.

Once you have chosen a thumbnail and spawn point, you can upload your layout to the workshop.
You will then see a message notifying you that the save is uploading.

You will then (after a small wait) either get a message that the upload was successful or failed (with an error message).

Workshop items can take up to an hour to become visible on the steam site, so don't be worried if your save doesn't show up at fist.

You can also update a previously uploaded workshop item in-game when playing both in VR and on PC.

Load the save that you want to update, then simply go to the "workshop" entry on the pause menu, then choose "Update layout".

Next choose one of your previously uploaded layouts to update.

From here you can set a new thumbnail if you choose to, and choose the spawn point for your updated layout.

Once you have chosen a spawn point, you can upload your layout to the workshop in the same way you would to upload a new layout, but it will instead update your previous layout to the new one.
You will then see a message notifying you that the save is uploading.

You will then (after a small wait) either get a message that the upload was successful or failed (with an error message).

Workshop items can take up to an hour to become visible on the steam site, so don't be worried if your save doesn't show up as updated immediately.