1. Click Edit, Image Properties.
2. Type values in the Horizontal and Vertical boxes.
·Enable the Identical Values check box to maintain image proportions while changing the resolution.
·High resolutions create very large files.
or, i found another way:
When you are in corel and you've got your image
dont do anything to the image, instead go to FILE and SAVE AS. A box will come up and make sure you change the file from a .bmp to a .jpg
Type in your file name and press save. Another small box will appear saying 'Jpeg export'. There is a scale called 'quality factor' which you can slide to achieve a smaller file! Hey presto! ( i had to do this several times however to achieve the right size file and one which is visible but it doesnt take long)