Re-texture a door way?

[PutraenusAlivius]

Select your model (right mouse button). On the bottom bar, there should be a text saying "Object Mode". Click it and choose "Edit Mode". If you already did that, press A. This should highlight all of the mesh.

Look at the right tab. Click the checkered floor icon. You may have to stretch the tab in order to see this. In the Image section, click Open and select your texture. Save. Export it as .dae with these settings (scroll down to do this).

APPLY MODIFIERS - Check
SELECTION ONLY - Optional (this makes the model that you select in the program to be exported.)
INCLUDE CHILDREN - Don't Check
INCLUDE ARMATURES - Don't Check
INCLUDE SHAPE KEYS - Uncheck this

ONLY ACTIVE UV LAYER - Don't Check
INCLUDE UV TEXTURES - Check
INCLUDE MATERIAL TEXTURES - Optional, but I usually left them unchecked.
COPY - Uncheck

DEFORM BONES ONLY - Don't
EXPORT FOR SECOND LIFE - Don't

USE OBJECT INSTANCES - Check it
SORT BY OBJECT NAME - Optional, but I usually leave them unchecked.

Export in your directory, set the name and done!