Saturate it then while it's moist cap it. It does a decent job of holding nutrients so root tabs and dosing can help supercharge it. It will also lower your pH certain degree and tint your water with tannins.
If you are just starting out, don't do it. The short reason: there is no way you can control the rate of decomposition. You will have your hands full with a new tank and unpredictable changes to your water conditions is the last thing you want to deal with.
Instead, look into innert substrates like Black Diamond sand, pool filter sand and so on.