Hi & Welcome to Linux Questions.
Congrads on you LM installation.-
The sound might be muted in the alsamixer. Open your terminal and type:
When you do you'll see multiple columns. Use your arrow keys to go to each column and raise up the master, pcm and etc. At the bottom of each column you should have what looks like this:
If at the bottom of the column you see [mm] that means it's muted.
To un-mute each column just type the 'm'.
When done close the terminal.
Hope that helps.
If you still don't have sound you may want to post what sound card you have so someone can help you with it.
To find out what sound card is on your mobo run this command: