How do I change my VNC session on lectura ?

Once you have managed to get a VNC connection to work correctly then you can modify how the unix environment looks by editing the file
.vnc/xstartup

an example of a startup file that would use KDE as the window manager would be:
#!/bin/sh

# Uncomment the following two lines for normal desktop:
# unset SESSION_MANAGER
# exec /etc/X11/xinit/xinitrc

[ -x /etc/vnc/xstartup ] && exec /etc/vnc/xstartup
[ -r $HOME/.Xresources ] && xrdb $HOME/.Xresources
 
xsetroot -solid grey
xterm -geometry 80x24+10+10 -ls -title "$VNCDESKTOP Desktop" &

xterm -ls -sb -sl 2000 -geometry 80x33-0-32 -ls -font lucidasanstypewriter-18 -name e &
 
startkde &

When using VNC you should be aware that if you have a screensaver set that is CPU intensive it will have a bad effect on the server machine (lectura) so you SHOULD change the default settings to BLANK.