Hi and welcome to the forum

the file you attached seems to bare no sesemblance to the example you stated above?

if you want D1 to be B1 * 2, then thats exactly how you enter it...=B1*2 you can then copy/paste that down as far as you need to

tip: if you look at the bottom right of the cell ther cursor is in (say D1) you will see the corner leeks like a small black square. If you aim the mouse at that small square, and then double-left-click on it, it will copy down to the 1st empty cell in C