I have a probem with the installation

HI, i bought the Photoshop in United State

The seller told me what if i install the program one time, i cant install it in my pc or another pc again

Accidentally i restored behind a time back the pc and a i lost the program and when i tried to install again i couldnt beacuse Adobe told me that the program I had already used it

What can i do to use it again?