cannot port forward

[#1]

I am trying to port forward an application but everytime I try to enter the "Translate to" IP address, I can only enter 5 characters, so instead of being able to enter 192.168.1.xxx I can only enter 192.1 then it won't let me enter anything else.
Has anyone encountered this problem before? If so, how did you solve it?
Thank you

[#2]

Can you give us an idea of which router you are using?

[#3]

Sorry, I forgot that crucial piece of info.
I am using the one plusnet sent me, namely: Thomson Gateway TG585 V8
Thank you

[#4]

If anyone has ever had this problem, please let me know how to sort it out
Thank you

[#5]

Quote

"Translate to" IP address, I can only enter 5 characters,

That text box is to enter the port you want it to translate to and not the IP. Take a look at the guides here:
http://portforward.com/english/routers/port_forwarding/Thomson-Alcatel/SpeedTouch585i/SpeedTouch585i...

[#6]

OMG, I feel like like a right plonker now.
Sorry about this.
Just had a baby boy 2 weeks ago and not getting any sleep, that's my excuse 
Thanks