After you create a bunch of UV textures, either by painting them yourself or by baking them from the mesh, you need a way to bring them back into Blender and apply them to your mesh. This process is where Image textures in your Texture Properties come in. Figure 8-12 shows Texture Properties with image textures on two different texture slots, one for a color map and another for a bump map.
The process for adding an Image texture is pretty similar to adding any of the procedural textures:
A File Browser opens, and it's where you can find the image you want to load as a texture. Alternatively, if you already have an image loaded, you can use this datablock to select that image by clicking the image datablock button on the left of the datablock field.
This step isn't critical, but it's something I like to do. Basically, it prevents the image from tiling. Because I'm loading a UV texture, I don't need it to tile.
This step tells the material to use your UV layout for texture coordinates to properly place the texture. Even if the image isn't the original one you painted in Texture Paint mode, as long as you painted the texture using the UV layout as your reference, it should perfectly match your mesh.
If the texture is just a color map, left-click the Color check box. If it's a bump map, left-click the Normal check box, and so on.