Hello!
Here (https://www.youtube.com/watch?v=5qFUilss-3U) is a tutorial I found for re texturing a rock which may help you out. <3 I also found a tutorial for adding textures to a mesh in Blender if you use it here! (https://feral-heart.com/smf/index.php?topic=46434.0) You may also be interested in this tutorial here. (https://feral-heart.com/smf/index.php?topic=60541.0)
Best of luck, fluff. I hope these can be of use to you.