My work has just stopped because I cannot figure out how to make steel. I have gold and coal and smelters but steel just isn't being made. Can anyone help?
Once you research either the 'Deep Mining' or 'Coal Furnace' upgrades from the workshop tab your game will start generating coal ('Deep Mining' produces it from mineral mining and 'Coal Furnace' produces it while you smelt iron).
Once you have enough (100 of each) coal and iron in your inventory, switch to the 'Workshop' tab, scroll down to the 'crafting' box and then click the 'steel' button to make your first steel.
Once you have some steel from that, you can either return to the same location to make more steel, or else click on the number links that appears to the right of the 'steel:' inventory item located in the lower left corner of your main screen. See the example screen below:
Click on one of the two circled locations above to make steel. Note the Workshop Tab.