How to upload 3d files?

Click the Import 3D File button and click the 3d file you want from your browser.

How to upload textures from 3D files?

Click the load images button and locate the folder with your textures. you don't need to click on individual textures.

How add and toggle textures on the model?

Select the object or objects then select the material. Toggle left and right to change the diffuse map of these.

How do I reset materials to default and fix blend errors?

Select the object or objects then select the material. Then click the clean materials button.