1) upload wordpress 2.6.2 files to server. make sure all files uploaded successfully.
2) change setting in wp-config.php, make sure the database information is correct.
3) visit the yourwebsite.com/wp-admin to proceed with the installation.

from your error, i seeing plugin error.. if this is fresh installation, plugin shouldnt 
be causing the error.. is this a wordpress upgrade? if yes, remove those plugin 
that might cause compatibility issue, then proceed with upgrade again.