I want to know how to import local images to specific places in a Blender 3D model

I am in a project for an advertising bicycle, I am somewhat new to this and I need to make a 3D viewer where outside the viewer I will have an interface to insert an advertising image into a 3D bicycle advertising box, here I did a test using a basic cube, but I want to do it on a 3D model of the bicycle, if anyone can give me advice or help me it would be a real relief, thank you

One approach is to separate the part of the model that you want your custom texture on, into a separate named mesh object, in your 3d modeller…

Then you export the whole model as .glb, you then load it in threejs, use somethng like

let loader = new GLTFLoader();
loader.load("url to your glb model.glb",(glb)=>{
    let themesh = glb.scene.getObjectByName("yourTexturedObjectName");
    themesh.material = new THREE.MeshStandardMaterial({
        map: new THREE.TextureLoader().load("url to your texture.jpg")

To find the part, and replace its material with your own material with the texture.