i created a 300 x 100 pixel image and put an image i found into it but it is wayyy to big, is there like grips to resize the picture? if so where are they or how do i turn them on lmao

Hit ctrl T for free-transform
remember to hold shift while dragging the corner anchor point inward.

click the transform checkbox when you click on the upper left arrow or your toolbar.
then hold shift while resizing to make sure its proportional.