I've made dozens of potions (poisons), equipped a weapon (for this example a steel mace, but have tried others), but can't figure out how to poison it. I go to my weapons inventory, the weapon is equipped but see no option or command to poison it. What am I missing?

Click on the poison and a dialog box will appear asking if you want to poison your weapon.

Alternatively, favourite it, then set a hotkey.

Click on the poison you want to use and that poison will used on the weapon that you are currently using.

If you have a weapon equipped then using a potion with a negative effect will apply it to the weapon in your right hand

Click on the poison in the potions tab. You won't drink it, you will apply it to your weapon.

What I want to know is how to poison both swords. Pretty much impossible from as far as I know.