Hi Sharon!
Welcome to
RP!
Images speak louder than words ... particularly in the line of jobs or hobbies most of us here have ... so, here is a practical example of what can be done
Attachment 1: Original photo 1 ... me taking picture from the roof terrace and being photographed at the same time ...
Attachment 2: Original picture 2 ... a nice beach full of penguins ....
Attachment 3: Combined pictures ... me + shadow, photographing the penguins while being photographed at the same time ...
As already said, it's a matter of accurate selection, copying and pasting, adapting for size, perspective, lighting/exposure,colour, contrast and sharpness, shadow (being very careful of the position of the light source) ... and I might have forgotten something ... but ... it can be done ...