You need to use the Photo software you have on your computer. Click the Help button for the software you have & it should have directions on resizing. Once they are resized you won't have problems. If you post what software you have someone here may have it & can help you also. Or someone may offer to do it if you email them to them.
With the program open of course, open the picture.
When the picture is opened,Left click on image,
go down to "Resize" left click once.
The resize screen will come up.
You have 3 options, I guess the fastest would be Pixel size, select that by clicking in the circle. Adjust the size to no more than 450 X 450, then, check the lower down on the screen to make the resolution is 72 pixels / inch.
Click okay, save your pic and give it a name, now you can post the pic.
If you have problems, email the pic to me, I will resize it for you.