First, Go punch a tree until you get a few sections of wood.

Second, make planks.  Select "I" for inventory. You will see 4 slots arranged into a 2X2 workarea grid. Place a section of tree in one of the slots to make planks.

Third, make a workbench from the planks.  Select "I" for inventory. You will see 4 slots arranged into a 2X2 workarea grid. Place one set of planks in every slot to create the workbench. Add the workbench to your available inventory then set it on the ground. You can break it apart later in order to move it to another location.

It occurs to me that you couldn't mine ore if you did not already know how to use the work bench to make the appropriate tools to mine the ore. Oh well...

Fourth, make a furnace. Select the workbench and click on it. You see a 9 slot workarea arranged into a 3X3 Grid. Place a cobblestone block into every slot except the center. A furnace will be the finished product. Add it to your available inventory and set it on the ground. It can be broken up for transportation like the work bench.

Fifth, follow the instuctions in the second post. You can also use coal as fuel. Using lava may not be possible unless you found a bucket in a dungeon. It takes iron bars to make the bucket otherwise (3 bars in a V shape). Fuel in the bottom slot of the furnace, ore in the top slot, bars are output.

You can make an iron block by placing 9 bars on the work bench so that one inventory slot will hold 576 iron bars at once. Just put the iron blocks on any workspace slot and it will produce 9 bars per block when you are ready for it.

You can produce Gold bars the same way you produced the iron bars.