Applying a UV map with material and texture

Hello everyone,

[There appear to be countless questions and responses that address this issue, but none seems to give me an adequate understanding of the whole process.]

I am creating a simple board game, which consists of a board with regular tiles. The tiles in the set will have a regular, repeating texture (plastic, wood or stone) with some sort of picture or design on them.

I have created my tiles and board (3D models) without textures in SketchUp, exported them as Collada (.dae) files, and imported them into Unity. This part is straight forward.

I would now like to apply the textures to the tiles and board from two different image files, if possible. For the tiles, the first would be the plastic, wood or stone texture, and the second a single .png with alpha channel that contains all of the individual images for each of the tiles or parts of the board. The board would be simple if I knew how to apply texture to the tiles, since it will only have one texture.

I understand the basic concept of UV mapping from my previous readings. I understand that I essentially 'unwrap' the three-dimensional surface to create a two-dimensional one. That is easy enough to do either graphically or mathematically. I understand that I need to assign the vertices of the component triangles to UV coordinates (0..1) to describe how the texture should be rendered on those faces. However, I don't know exactly how to apply this to Unity. At this time, I have my .png files for the textures, and I have my 3D .dae files for the models. As such, I should be able to attain a coordinate representation and specify how the coordinates/faces of my models should relate to my image files. However, I simply don't know how to do this.

Would anybody be able to step me through what I need to do to apply my textures to my models and fit them properly?

Thank you in advance.