How to use '{{< yield}}' and to display the right template

I’m trying to add iron router to my website and the problem I got is

my template calling {{> templateName }} no longer works

I join the code of body.html where I call mostly all my templates. I’ve read that I should use {{> yield}} but I don’t understand how it will display the right template and what I need to do to re-use my templates…

lib/router.js

Router.route('/', function () {
  this.render('acc');
});

imports/ui/body.html

<template name="acc">
<body id="pageAcc">
  <div class="container">
    <header>
<h3 id="titreRecherche">Rechercher un article </h3>
      <form id="tfnewsearch">
       <input type="text" class="tftextinput" id="tftextinput" size="35" maxlength="120"><input type="button" value="search" class="tfbutton">
      </form>
      {{#if currentUser}}
      <div id="whereAmi">
        <span title="En cliquant sur ce bouton vous accepter d'ajouter votre localisation dans les informations de l'article"><button type="submit" class="posBut">Me localiser</button></span>
      </div>
      <div id="mesArticles">
          <button type="button" id="showMesArticles">Afficher mes articles</button>
      </div>
      {{/if}}
      {{#if wantLoc}}
      <div id="instagramFeed">
          <button type="button" id="goToInstagramFeed">Afficher les photos de v__jerome</button>
      </div>
      {{/if}}
      <div id="connexion">
        <button type="submit" id="loginLink">{{> loginButtons}}</button>
      {{#if currentUser}}
      {{#if wantLoc}}
        <p>Vous êtes à: {{where}}</p>
      {{/if}}
      {{/if}}
      </div>
      {{#if currentUser}}
          {{> ajoutement}}
      {{/if}}
    </header>

      {{#if wantInsta}}
      <div id="IF">
        <h1 id="titreInsta">Les photos de v__jerome</h1>
          {{> instagramfeed}}
      </div>
      {{/if}}
    <h1 id="titreListe">Les articles</h1>
    <ul id="lesArticles">
      {{#each articles}}
        {{> article}}
      {{/each}}
    </ul>
{{#if wantModif}}
  {{> modify}}
{{/if}}
{{#if currentUser}}
{{#if wantLoc}}
<div id ="map"></div>
<script async defer
  src="https://maps.googleapis.com/maps/api/js?key=myKey&callback=initMap">
  </script>
{{/if}}
{{/if}}
  </div>
 <a href="#" class="scrollup">Back to top</a>
 <input type="hidden" id="nextArt">
</body>
</template>

imports/ui/body.js

import { Session } from 'meteor/session'
import { Template } from 'meteor/templating';

import { Articles } from '../api/articles.js';
import './article.js';
import './body.html';

import './ajoutement.html';
import './modify.html';
import './instagramFeed.html';

Template.body.onCreated(function bodyOnCreated() {
  Meteor.subscribe('articles');
  Session.set('insta',1);
  Session.set('showArt',1);
});

Template.body.helpers({
  articles() {
    return Articles.find({}, {sort: {createdAt: -1}});
  },
  wantModif: function() {
    return Session.get('wantModif');
  },
  
  [then a lot of Template.body.helpers ]

And that’s all I did. Can someone help me to use my templates again ?