Help Mapping texture TW

Hello everybody,
I’m a new TW user and I’m trying to figure out how best to work with this great program …
If I want to apply a texture on a TW material is there a way to manage the alpha channel?
To explain me better eg: if I want to apply a logo on a glass that is not a full shape but a drawing in a texture in .png and I need to see both the glass and the writing.
How should it be managed in the program?