The following is taken from the Pligg Beta readme.txt
#######################################################
################## INSTALLING #########################
#######################################################
1. Create a mysql database. Example "pligg."
Note - Have your database name, username, password, and
host handy before installing
2. Rename settings.php.default to settings.php. Do the same
for /libs/dbconnect.php.default.
3. Upload the files to your server.
4. chmod 777
/avatars/user_uploaded
/backup
/cache
/rss/templates_c
/templates
/templates_c
5. chmod 666
/libs/dbconnect.php
/libs/lang.conf
/libs/options.php
settings.php
6. chmod 655
config.php
7. Open www.<yoursite>.com/install/ in your web browser.
Step 1: Make sure to read the entire page and click continue
at the bottom when finished
Step 2: Fill out your database name, username, password, host,
and your desired table prefix.
Step 3: Make sure there are no error messages!
8. Delete your /install folder.
9. chmod 644 libs/dbconnect.php
10. Open www.<yoursite>.com
11. Use the god account. Login: god - Password: 12345 to make the changes needed.
12. Change the password from 12345 to something different as soon as possible.