ok i have had valve hammer for a couple of months now. i havent used it in like 2 months though. when i tried to use it just before i started a new map. i would make a floor of a certain texture. then i would click the browse button to look through all the textures(the one that goes full screen when you click browse). say i had a brick texture as my first 1. if i got and click on another texture it would just stay the same. so basically my textures wont change. not sure why.

Once you pick the texture you have to select the brush and hit the button that looks like a block covered in a birch texture, it is next to the button that has the pop-up texture application tool.

On the left side of the editor you will see image buttons lined from top to bottom. Roll your mouse over them, and when you get over the one that says Apply Current Texture, hit that when you have a new texture selected.

you need to make sure that the brush that you want to apply a texture to is selected (highlighted in red) then hit the apply to texture button. i know it may seem stupid to you, but sometimes the easiest things are overlooked, and if this wasnt the case, im not trying to make you feel silly