As the title says, I know that there one time was a download button to install spotify but i dont have it. Is there something else you have to do for 1.2?
I downloaded it from www.clementine-player.org, I also tried it in arch just to see if it worked there but same problem.
You can try to install the spotify plugin manually from the clementine repository.
You should grab the last blob & libspotify.so files.
1) Close Clementine application.
pkill clementine
2) Intall wget to download the plugin.
sudo apt-get install wget
For 32-bit
3) Create the folder structure for the plugin.
mkdir -p -m 775 ~/.config/Clementine/spotifyblob/version14-32bit/
4) Go to the plugin folder.
cd ~/.config/Clementine/spotifyblob/version14-32bit/
5) Download the plugin.
wget http://spotify.clementine-player.org/version14-32bit/blob
wget http://spotify.clementine-player.org/version14-32bit/libspotify.so.12.1.45
6) Give the correct perms to the plugin.
chmod 775 blob libspotify.so.12.1.45
Edit as per relaytheurgency comment
7) Rename the libspotify.so.12.1.45 to libspotify.so.12
mv libspotify.so.12.1.45 libspotify.so.12
For 64-bit
3) Create the folder structure for the plugin.
mkdir -p -m 775 ~/.config/Clementine/spotifyblob/version14-64bit/
4) Go to the plugin folder.
cd ~/.config/Clementine/spotifyblob/version14-64bit/
5) Download the plugin.
wget http://spotify.clementine-player.org/version14-64bit/blob
wget http://spotify.clementine-player.org/version14-64bit/libspotify.so.12.1.45
6) Give the correct perms to the plugin.
chmod 775 blob libspotify.so.12.1.45
Edit as per relaytheurgency comment.
7) Rename the libspotify.so.12.1.45 to libspotify.so.12
mv libspotify.so.12.1.45 libspotify.so.12
8) Open Clementine and go to Menubar > Tools > Preferences > Internet providers > Spotify to set your account.
Before:
After:
NOTE: In this example I'm running Ubuntu 13.04 64-bit with Clementine 1.2
Hope this helps.