You really should read the manual but Im feeling generous so…
click on the object you want to change
in the material tab at the bottom you should see the name of the material
on the left of this is a double arrow, click this and a drop down appears, choose add new
now I suppose your problem is you’ve used the default material - called material added a texture then as you create new materials they are also linked to the initial material
The easiest way of putting this right is just to go to the object you want a different texure for and in the texture tab choose add new to replace the link to the original texture to a new copy. Then just change the settings
The key thing to realise is that the material instances and texture instances are ‘global’ as in you can re-use a texture from one object without having to make another copy.
I tend not to use the default block ‘material’ and instantly create new materials for each of my objects. That way I can create a new copy of the default settings by picking the new object, changing materials to the ‘material’ default then choosing add new to create a stating copy. Otherwise you have to make a copy of a material you may need to remove all the settings you dont want.
add new makes a copy of the current settings
changing to a previously setting makes a link (change it in one place it changes all objects using it)
this applies to materials and textures