I have a raspberry pi 2 and installed the Raspbian Version from 2015-05-05.

As "boot option" I chose "Console Text console..." because I don't want a full desktop.

I logged in from my remote PC via SSH (putty). I want to start Firefox but get the following error:

    root@raspberry:~# firefox
    
    (process:2425): GLib-CRITICAL **: g_slice_set_config: assertion 'sys_page_size =                                   = 0' failed
    Error: no display specified


If I try to start xclock I also get an error:

    root@raspberry:~# xclock
    Error: Can't open display:

I want to start the programs on my display connected via HDMI.
Even if I do this directly on my raspberry console it doesn't work.

How can I tell my raspberry to display this programs on my via HDMI connected Display?