How do I add ACS psf fits files generated using tinytim to another fits image to create a simulated image. The idea is to add the generated psfs to the image and then deconvolve it. I hope to use any movement of the generated psfs in the deconvolution to judge the effectivness of the deconvolution

Have a look at the MKOBJECTS task in the ARTDATA package. Specifically, the 'star' parameter can specify an image to be used as the PSF. Post back if this doesn't do quite what you want.Cheers,
-Mike