First off I am a new comer to the actual Bethesda site, but been a fan Since morrowind, and brand new to modding!

Thanks for taking this time to read my problem. I am following the tutorial on step 2, while I am piecing the nordic walls/floors together, they don't become flush with one another. Instead it leaves a gap between the pieces, and when I try to move it closer, it just overlaps. I hope I explained this right, but I am having a hard time following the instructions when I have this problem, and I am sure it's a simple fix... thanks in advance!

Make sure that the walls on either side of a room are in fact side pieces, and that the walls at the top and bottom are front pieces.

If you have confirmd this, you may need to rotate your mid pieces so that they connect. with front and side walls correctly. It matters wich angle some pieces are facing.

You will also experience this with hall end pieces with doorways. And even more when dealing with cave pieces.

Is snapping turned on? if it is and U'v still got this issue then chuck sum clutter or sumthing in the gap:) It works!
also, the set is made up of specific peeces in relation to where thar placed like, leftwall, rightwall, fronwall and back (Those aint the proper names but I'm sure u no that already)

I recently thought I'd try my hand with building a cave system with the epic set... I got gaps all over the place! but the cave is looking great.

The usual issue is your angle on the tile pieces are not the same, or are a bit off.
For example, one could have a Z rotation of 90.0500 and the other could have a Z rotation of 89.1200. The will never line up together and will leave a gap.

Right click in the render window and select "Render window properties".
On the movement tab, make sure "snap to grid" is checked and then set the value to something like 64.
Turn on snap to grid by pressing the button in the main toolbar (6th one from the left)
Things should then snap together a lot better.

I am brand new too (at part 3 ). Make sure you have snapping turned on. Then make sure that you don't try to set sidepieces with frontpieces. One of those two should do the trick.

Also, make sure that your snap to angle value is 45.

Thanks for all the helpful tips! I went to the beggining of the video, and re-did my cell, and positioned everythin to 0, now everything fits together no spaces! I am very happy this is fixed! I have no idea where I went wrong, but I must have either missed a step, or something wasn't set properly.

Probably the latter. Welcome to the community.