Left click on gold, potions, equipment or other items in the world where the default action is to pick up. For containers, drag and drop onto the character's portrait in the top left of the screen, or right click and 'pick up'.
To move containers, there is an issue if you just left click and hold without moving the mouse, where the cursor will switch back to the normal game cursor. You need to click and move the mouse all in one motion, or click while already moving the mouse slowly. That will allow you to move containers (that you have the strength to move), with the cursor changing to a hand icon and the item highlighted in white (if you can move it there) or red (too far/heavy or blocked).