If you head over to editor.construct.net and just search through the beginner's/intermediate/advanced examples sections there are plenty of tutorials on how to build a top-down view 2d game, beginning with making sprites and creating their animations and setting their controls to building the world around them. Also as you move through and have specific questions just try googling said specific questions because odds are there is a tutorial on the problem you are facing, and of course the forums. (literally on front page of Beginner's Examples there are two tutorials just for top-down view games, and you can also open the games they have on their Start Page section and play around and explore how they were created).
With the pond I would create an object to represent the pond, an object to represent the waves, and an object(s) for fish. for the pond I would basically just make a blue splotch of water that had rippling/moving edges, youtube videos of ponds/lakes/rapids/etc... pick what you want it to look like and then just emulate those movements in the animations. So if you were doing a dead quiet pond it probably wouldn't move that much unless it had something influencing said movement (jetskis, boats, etc...)
but if you were say doing an ocean for example then you would want to make the edges of the water spread out and then recede back in repeatedly over the beachfront.
The rippling waves I would just make the object then literally paint the ripples spreading outward each cell so it appears they are moving out from the spots where the ripples are created toward the edges of the pond.
then the fish (I mean this also depends on the type of behavior you want them to have, IE do they jump out or are they just visible under the surface? for instance) but I would just make it so they have a swimming animation which is their idle, then have a jumping animation for when the are "jumping" out of the pond.
I would start with "How to animate objects in Construct" tutorials for most of that stuff, will help you understand how to utilize the editor immensely.
And GIMP is a great free digital drawing software that you can use to create all this, specifically if you wanted to make it so you can see through the water (making it slightly transparent or opaque) GIMP can help you accomplish that.