Hi saphrona,
You can either squeeze the image. Than try to add this to your css:
#slider .wp-post-image, #slider .entry-attachment {
height: 200px;
}
or you can try to reduce the slider heigth only, which keeps your image proportional but croppped from the bottom:
.slides {
height: 200px;
}
In both cases you need to adjust the native images unless you’re happy.