A much easier program to create subtitles is with AEGISUB.

This is available from http://www.pardususer.de/Community Depot/pardus-2011/ (only for Pardus 2011)

Making a new subtitle file for Subtitle Composer.

As Subtitle Composer can not create a new empty subtitle file, open a new file in Kwrite and copy/paste

1
00:00:00,000 --> 00:00:00,000

including a <enter> (or CR) at the end of line 2.

Save this file as any_name.srt

Creating a combined video-subtitle file.

Use Avidemux (GTK) to combine the source video file and the subtitle file

The settings which I use with my Canon PowerShot A430 are (they can be used as a starting point):

Video     > MPEG-4 ASP (Xvid)
Configure > Main          > Encoding type: Two Pass - Average Bitrate
          > Motion & Misc > no mark at As Input 13:9
Filters   > Subtitles > Subtitler (srt/sub) > + > browse and select the .ass file
                                                > Font (TTF): /usr/share/fonts/bitstream-vera/VeraSeBd.ttf
                                                > Encoding: Latin-1 (Western European)
                   or > ASS (ass/ssa) > + > browse and select the .ass file
Audio     > Copy
Format    > AVI

The result of the settings can only be viewed in the with "Save" generated name.avi file