Umm.
First, you have to align the individual buildings so that they fit into a 32x32 grid. Think of the whole image as an invisible chessboard, and your buildings must always stand in a single column, with base of their ground tile touching bottom of some of the "chessboard tiles". The attached image shows exactly that. The blueish background is exactly the one needed, yours was a bit off

The pink is there just to show the "chessboard", you'll have to fill it with the other colour to be transparent, too.
Second, you will want to write a dat file for these houses. You can take a look at existing .dat files, they are plain text which contains info about the building. There's a
page on wiki on that, and you will want to look at
image references, too. I've attached an example that works with the first two houses, so by comparing the actual thing and wiki you should be able to understand...
Next, you will have to get makeobj, a console program that compiles dat+png into pak files. Just run it as "makeobj pak32" in the folder with the two files and you should get two paks. I'm not sure if the whole console thing - path, running programs with parameters and working folder - is something you know, but I'll just assume that yes for now...
What you have so far + these three steps should yield pak files, which is more or less our "victory objective" here

To answer the question about templates etc.: I think there aren't any templates for this pakset. However, it's really easy to draw at least houses in this size. I assume you took the original picture from
this page (btw, no problem with that), and the one thing that you can see is that most other buildings are drawn at "angle". Simply draw straight lines as 2:1 - two pixels horizontally, one vertically. This is the "default" orientation, the one building you changed is different
