add a Point to a renderd Vectorlayer openlayers-7

Question

how to add a feature to a exist layer on map , openlayers-7 this is my code : I defined a vector Layer named myJson and i want to add a Point to this layer in code how can i achieve that ?

const myJson = new VectorLayer({
  source: new VectorSource({
    format: new GeoJSON(),
    url: 'geo.json'
  })
})

map.addLayer(myJson);

 const P1= new Feature (new Point(coordinate));
        myJson.addFeature(P1);