ChemLab is overhaul mod: it changes vanilla mechanic and because of this there are some things to consider:
1.ChemLab recipes are resource sinks. This is not to provide frustration. This is intended to provide more social aspects to SMP.
2.ChemLab machines are energy sinks. This opens gameplay style involving BuildCraft kinesis pipes and gates to a full potential.
3.ChemLab adds their own tier progression and intermediate tiers to vanilla mechanics(Iron Ore is smeltable to Wrought Iron, not commercially clean iron as it was)
If this doesn't freak you out - congratulations, you have engineer mind which can destroy all obstacles with ease.
To be successful in harsh ChemLab world you need to start to collect resources. First you build stone pickaxe to extract some iron which will make it to Wrought Iron Pickaxe. Due to structural weaknesses it is not much durable, but good for collecting delicate resources(diamonds, gold).
That slag-embedded iron is not so effective in constructional works so you need to slightly increase outcome by grinding it to fine particles. Time to build your first machine: CRUSHER! Consult NEI or CraftGuide for recipes. This machine will be hard to complete because of enormous wrought iron consumption. It needs at least TWO BuildCraft Stirling Engines to run, but first you need to assemble the HARDWARE PROGRAMMER - your communication gateway to machines.
Just drop programmer onto slot with pins to open its GUI. Second tab(with arrows) allows you to select recipes.
You can't change recipe if there is something in a machine already.
You need to replace it, but you will lose all items and power in it.
Select the one which grinds Iron Ore. That way you will get double of the Wrought Iron output.
Success! Now you need to develop your production lines to get access to more resources and eventually to a clean Iron. Check the production lines section and start your business.