Where Do I Actually Buy The Items?

[Excalibur--prime]

I feel like a total idiot but ive looked everywhere on steam and in the arsenal and i just cant seem to find any of these new items for sale. what am i doing wrong?

[(PSN)IIIDevoidIII]

As far as I'm aware, they should be available on the Warframe Market on Steam. 
I believe there is also a link somewhere in the in-game Market that takes you to the Steam location, but a PC Tenno would have to verify that for me.

 

Moved to Players Helping Players.

[Demonfr34k]

Go to the market there should be a new icon with the steam icon, if your not running warframe downloaded through steam you wont see this or the items available for sale.

 

You should also be able to see them in arsenal if you've launched through steam.

Edited December 21, 2015 by Demonfr34k

[taiiat]

you will need to be running Warframe through Steam to get the ability to purchase these for the time being.

[Excalibur--prime]

well that must be my problem. I have a steam account but i play warframe independent of it now

[7Lions]

log into WF via steam and you'll see the options to purchase the steam skins.