在模块中导入“ReactiveFormsModule”模块，并在相关组件的模板中添加“formGroup”指令。示例如下：

app.module.ts：

import { BrowserModule } from '@angular/platform-browser';
import { NgModule } from '@angular/core';
import { ReactiveFormsModule } from '@angular/forms';

import { AppComponent } from './app.component';

@NgModule({
  declarations: [
    AppComponent
  ],
  imports: [
    BrowserModule,
    ReactiveFormsModule // 导入ReactiveFormsModule模块
  ],
  providers: [],
  bootstrap: [AppComponent]
})
export class AppModule { }

app.component.ts：

import { Component } from '@angular/core';
import { FormBuilder, FormGroup } from '@angular/forms';

@Component({
  selector: 'app-root',
  templateUrl: './app.component.html',
  styleUrls: ['./app.component.css']
})
export class AppComponent {
  form: FormGroup;
  
  constructor(private fb: FormBuilder) {
    this.form = this.fb.group({
      // 定义表单项...
    });
  }
}

app.component.html：