Equipping crew. I have new armour and customzation items for my companian, but can't equip them , how do I do that.

I find the easiest way (and used to be the only way) is to open your character panel (default C), click on the companion tab, then right-click on the item in your inventory or drag it from the inventory to proper slot. You have to have the companion summoned for this method to work unless you are on your ship. This is also how you equip items to your ship but you choose the ship tab, of course. If you are on your ship and you wish to equip a companion, you follow the steps above but after you switch to the companion tab, you cycle through your companions to find the one you need, then right-click or drag the item from inventory.

 

You can also shift+right-click, I believe it is, the item in your inventory and it's supposed to equip to your currently summoned companion but I've had that work unreliably.

And remember you can equip companions with your cast off gear as long as it is of a suitable type. You should only do this if the companion shares the same main stats as you