To render a simple shape with a 2D texture, use the following steps: 

1. We'll define a simple (static) function for loading and initializing textures: 

GLuint Texture::loadTexture( const std::string & fName ) {
  int width, height;
  unsigned char * data = Texture::loadPixels(fName, width, height);
  GLuint tex = 0;
  if( data != nullptr ) {
    glGenTextures(1, &tex);
    glBindTexture(GL_TEXTURE_2D, tex);
    glTexStorage2D(GL_TEXTURE_2D, 1, GL_RGBA8, width, height);
    glTexSubImage2D(GL_TEXTURE_2D, 0, 0, 0, 
              width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);

    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, 
    GL_LINEAR);
    glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, 
    GL_NEAREST);

    Texture::deletePixels(data);
  }
  return tex;
}

2. In the initialization of the OpenGL application, use the following code to load the texture, bind it to texture unit 0, and set the uniform variable Tex1 to that texture unit:

GLuint tid = Texture::loadTexture("brick1.png");

glActiveTexture(GL_TEXTURE0); 
glBindTexture(GL_TEXTURE_2D, tid);
 
// Set the Tex1 sampler uniform to refer to texture unit 0 
int loc = glGetUniformLocation(programHandle, "Tex1"); 
glUniform1i(loc, 0); 

3. The vertex shader passes the texture coordinate to the fragment shader:

layout (location = 0) in vec3 VertexPosition; 
layout (location = 1) in vec3 VertexNormal; 
layout (location = 2) in vec2 VertexTexCoord; 
 
out vec3 Position; 
out vec3 Normal; 
out vec2 TexCoord; 
 
// Other uniforms...
 
void main() 
{ 
  TexCoord = VertexTexCoord; 
  // Assign other output variables here... 
}

4. The fragment shader looks up the texture value and applies it to the diffuse reflectivity in the Blinn-Phong model:

in vec3 Position; 
in vec3 Normal; 
in vec2 TexCoord; 
 
// The texture sampler object
uniform sampler2D Tex1; 
 
// Light/material uniforms...
 
void blinnPhong( vec3 pos, vec3 n ) { 
  vec3 texColor = texture(Tex1, TexCoord).rgb;
  vec3 ambient = Light.La * texColor;
  // ...
  vec3 diffuse = texColor * sDotN;
  // Compute spec...
  return ambient + Light.L * (diffuse + spec);   
} 
void main() { 
  FragColor = vec4( blinnPhong(Position, normalize(Normal) ), 1 ); 
}