Room resolution please help

[ggp]

This may be simple, but i really am stuck.
I only had windows paint so have downloaded a 60 trial paint programme called Topdraw. Its a good programme, but my problem is that in the AGS tutorial it talks about game resolutions and i have started my game in 320 x 200. The tutorial says to make sure when you draw your backgrounds they are done in this resolution, but how do i change the programms resolution ? The only options i can see are paper sizes;A4, A5 etc. How do i set it for 320 x 200 ?! It was exactly the same in MS paint, so i realise there must be an easy explanation.....

[Radiant]

Here's an easy way to go about it...
open MS Paint. You should get a white rectangle that you can edit.
Click 'image', then 'attributes'. This allows you to specify the image's size. For units, select 'pels' (short for pixels). Select 320 by 200.
Save as bmp. Open in Topdraw. Ta dah!

(the tricky part is that some programs use a DPI rating, which technically is also the image's resolution but is not important for AGS - we want a resolution in pixels)

[ggp]

Think it's sorted now - thanks for your help