how to link 2 togther account here ?

how to link 2 account here ? i try to Associate them but it ask me to POST first ?

 

What're you talking about?
1)Associating multiple Steam Accounts?
2)Or is it you intend to include in your Forums Profile external links e.g your very own website, YouTube channel, Facebook(wouldn't recommend you that) etc.
If you are talking about 1) I don't think that's possible .. You can associate one Steam Account per Forums Profile.
As for 2) You can insert links in the drop-down bar where your name is on the left part of the screen, forward to Personal information.. That's where you can fill in various info such as Location, Occupation, About Me etc...
Hope this helps!