Textures can be tricky when you are unfamiliar with them! I will try to give a basic walkthrough on how to work with them.
This tutorial is written for LNZ Pro. It will also work very similar in ResHack, but not so well in older hex programs, though you may still get something out of understanding how it all works, perhaps!

You find textures pretty far down in the file. It will look different depending on your breed, but the basic layout is the same. It may look something like this:
[Texture List]
\art\textures\hair10.bmp 1
\art\textures\swtr7.bmp 1
\art\textures\jowl2.bmp 1

So what does this mean? Basically, the first part is the pathway for the program, telling the game where the texture is found. As long as you want to use an internal texture, you want to keep the whole Art\Textures bit. If you want to use an external furfile, you change it to where you put the furfile. Most people put them in the respective species/breed folder, meaning the path will be Resource\Dogz\name.bmp (or catz, if that's your program).
The second number is a very nifty thing! It tells the game what colour in the texture is to be transparent. It works like this:
0 - Everything is transparent. The entire texture shows through. The clothes that show patterns, like the zebra pants, are like this.
1 - No transparency in the texture; it will show under the colour. Most default petz textures are like this.
All other numbers are used to define which colour on the texture should be transparent. For instance, if the texture is black and grey and you want the black parts to be transparent parts in the game, you can put in a number like 35.

Assigning textures
When you want to assign textures in the game, you need to know the texture numbers. Now, strangely enough, the first texture is not #1, but #0. So if we use the example above, hair10 is texture #0, swtr7 is #1 and jowl2 is #3.
When it says for instance 10th number, it means the 10th number listed on that line, starting from the left, first number listed being #1.

So where do you change texture? It's pretty simple, really. Here is where to find it in the different sections:
Addballz: 14th number - the very last number
Colour Info Override: 4th number. Normally you just list ball and colour, right? Add in a third and fourth number. The 4th will be texture (the 3rd is Group, you can usually ignore it, just put 0).
Paint Ballz: 10th number - the very last number.
Ballz Info: 8th number - the 2nd last number.

If you ever get uncertain, check above the sections. Unless a hexer has removed it, PF Magic has usually provided a helpful little list, such as this one above ballz info:
;Color,outline color,speckle color,fuzz,outline type,size difference,group,texture,ball number
It tells you exactly what numbers mean what, see? These lists are your friends!

Tips on creating your own textures
Here are some tips that you might find helpful if you want to make your own textures!
- In Petz 5, all textures must be 32 x 32 pixels, or these multiplied (such as 64 x 64 etc). Even if you you're not making your texture for P5, I recommend to stick to these measurements - you never know when you or someone else would like a copy that works in P5!
- All textures must be 256 colour mode (not 24-bit etc). Also, remember that petz only understands a certain colour palette, so it's best to stick to true petz colours. Use a colour list for comparision. Even then, the colours may change in the game. Sometimes you're lucky and it looks great, and sometimes it doesn't... Just keep trying!
-Try to make your texture tile well, or it will look blocky in the game.

Here are some common texture-related problems.
- Say that a section of the file is listed to use texture #4, but your texture list only goes up to #3 (or any number lower than 4). Chances are the game will crash. If your game suddenly crashes and you're not sure why, try to make sure you've listed the textures correctly.
-If the texture looks odd, make sure you've set the transparency correct
- If you get no texture, the pet looks flat, make sure that A) the path is correct, B) the transparency is correct and C) that it is a 256 colour bitmap.
- For all Petz 5 textures, make sure the size (32 x 32 or these multiplied) is correct, or the texture won't work, and may crash your game!