Go to www.soundcloud.com
Click on 'Create account' over there on the right:
Then choose to log in with Google or Facebook or your email address:
And you're in - clicking on 'Upload' over there in the top right is where you can load new sound clips.
And if you want to share a clip, you come down to where it says 'share' underneath the clip itself:
That will open a pop-up window, and you just need to copy the url at the bottom of that window and then paste it into your post in the forum.
For a quicker and faster experience with uploading sound clips, get the Android app here:
or the Apple app here:
and you'll be able to record straight into your mobile phone, and it will upload automatically (you'll still need to go through the steps above to share it to the forum, though).
Any questions, fire away...