When I want to install a software, it will tell me :
Insert ‘openSUSE -12.3 -1.7 (Disc 1)’
What happend and what should I do?
When you install openSUSE, it adds software sources in yast.
One of those sources is the dvd you used to install opensuse.
You can delete this source from yast, or insert the dvd. 
zypper lr | grep 'openSUSE -12.3 -1.7 (Disc 1)' | cut -d'|' -f 1 | xargs sudo zypper rr
This thread is now closed and will be moved to the english forums in 10 minutes.
One of the things that I do, soon after installing, is:
Yast → Software Repositories
There, I select the repo that refers to the install media, and uncheck the “enabled” flag (near the bottom of the screen).
Once that repo is no longer enabled, you won’t be prompted to insert the DVD.