Both the script and animation are inside the walk replacer but it is not working.

Ok, please check the following...

a) Are scripts enabled on the land you are on, if scripts are disabled it may not work.
b) Perhaps the scripts need resetting or have stopped. Try the following steps...

  i) Drop your item on the ground.
  ii) Right click on it and select edit to go into edit mode.
  iii) Now go to the tools menu at the top of the screen and select the option from it 'Set Scripts To Running'
  iv) Now go to the tools menu again and select the option 'Reset Scripts In Selection'

How do I put the walk inside the walk replacer?

a) Drop the walk replacer on the ground in front of your avatar
b) Right click on the walk replacer and select edit
c) On the window that pops up go to the content tab
d) Now drag the walk animation from your inventory into this content window
e) If you now take the walk replacer into your inventory and attach it it should work.

IMPORTANT: MAKE SURE YOU DO NOT REMOVE THE SCRIPT THAT COMES INSIDE THE WALK REPLACER LABLED 'walk'. THIS SCRIPT IS ALSO REQUIRED FOR IT TO WORK.

I bought a walk replacer and all I see is a blue ball on my back....

This will happen if you took the script out of it called 'walk' the walk replacer requires this script, and the animation you wish to replace your walk with to be in its contents.

I bought this walk replacer and it just gives me the message 'Abranimations Walk Animation Not Found' or similar..

My walk animations come with separate walk replacer objects. If you wish to use the walk replacer instead of your own animation override, you will need to put the animation inside the walk replacer objects contents. If you do not, it will not be able to find the animation and will give this message.