Always make a backup of your equipment file before you "experiment".
Part 1: Add unit in equipment file.
For example: There is a unit called Italian_Bruckenpioniere that you would like to include in your project

Filename: Italian_Bruckenpioniere.png
First step, open the equipment.pzeqp file which is located in the \data folder with notepad, notepad++, excel...whatever suits best for you.

This is what you see. Unit names followed by a lot of numbers. These are all different categories which are explained on the top of this file (the ID line)!
When adding a new unit, add it to the bottom of the list. It is not recommended to put it in a reserved slot of the vanilla equipment file.
The last unit is at line 1521:
1521 Landing Craft 16 80 7 60 4 1 0 1 0 0 -2 0 2 2 1 3 26 West_Allied_Landing_Craft.png 1.1.1940 1.1.1946 6
Your new entry could be 1522 but you don't have to. Let's say you will have a whole bunch of italian units you want to add so perhaps you can start them off at line number 2000

We chose the place and the name for the unit. What's next? The other parameters ofcourse. The best is to copy a line of a unit of the same class as the unit you want to add.
Here we are lucky , the germans have a bridge engineer. So... let's copy and paste the line.
Then we get for line 2000:
2000 Italian Bruckenpioniere 0 113 5 0 2 2 0 1 2 1 -1 1 8 17 2 0 0 Bruckenpioniere.png 5.4.1939 1.1.1946 11 beng close Bridge

Is that all? Not yet. You will have to change at least two things. The nation code and the unit png name.

Encircled in red is the nation parameter, encircled in orange is the unit png name. Let's give it the correct values.

The nation code for Italy = 5 and the name of our png file is Italian_Bruckenpioniere.png
The other values can also be changed but is personal preference. You can change the cost, movement, soft and hard attack, availability and much more. Now you can save this file.
Part 2: Add unit in efx file.
Our friend received his stats but if you don't add the Italian_Bruckenpioniere to the efx file, he is not going to make a sound. Also backup your efx file! The file is located in the \graphics folder.
You can open the file with the same program as you used for the equipment file.

That is how it looks like.
Now we need to add our unit. New entries should be added to the bottom of the list.

Now i am going to use the same trick. Copy and paste the data from the german unit.

Then you can save the file.
Part 3. How to use your new unit.
It is better to load your project with its custom equipment file and efx file into GME. In my example it's a project's name which contains the Italian_Bruckenpioniere

Then launch the scenario editor. Open your project's scenario, chose units and chose Italy ofcourse. (better untick the box show only units for this scenario for test purpose)

It is there. At least we know we entered the correct name in the equipment file. If you only see the name but no picture, than you made a typo in the *.png file in the equipment roster or just simply forgot to exchange for the right *.png name.
To be certain if it is correct in the efx file, you will have to actually try out your scenario in the game and listen if it makes a sound. About correct animations, you'll have to ask somebody else.
Hope this was useful.
