How to implement 1 : M relation in ActiveAndroid library?

Question

Android

I use the ActiveAndroid library as a local database.
there is a Post model

package smartfoxlabs.ppos.Models;

import com.activeandroid.Model;
import com.activeandroid.annotation.Column;
import com.activeandroid.annotation.Table;

import java.util.ArrayList;
import java.util.List;

/**
 * Created by dwite_000 on 24.10.2014.
 */
@Table(name = "posts")
public class Post extends Model {

    @Column(name = "postID",unique = true)
    public int id;

    @Column(name = "type")
    public String type;

    //WTF?
    @Column(name = "slug")
    public String slug;

    @Column(name = "url")
    public String url;

    @Column(name = "status")
    public String status;

    @Column(name = "title")
    public String title;

    @Column(name = "title_plain")
    public String title_plain;

    @Column(name = "content")
    public String content;

    @Column(name = "excerpt")
    public String excerpt;

    @Column(name = "PostDate")
    public String date;

    @Column(name = "Category")
    public java.util.List<Category> categories;

    @SuppressWarnings("serial")
    public static class List extends ArrayList<Post> {

    }

    public boolean exists() {
        boolean flag = false;
        //Post post = new Select().from(Post.class).where("Min = ?",this.id).executeSingle();
        return flag;
    }

    public Post() {
        super();
    }
}

there is a Categories model

@Table(name = "Categories")
public class Category extends Model {

    @Column(name = "Mid")
    public int id;

    @Column(name = "slug")
    public String slug;

    @Column(name = "title")
    public String title;

    @Column(name = "parent")
    public int parent;

    public Category() {
        super();
    }
}

A Post can have several categories, so when I call save, for some reason it does not save the list of categories for Post.
UPD: as I understand it, I still have an M : M Relationship, since a Post can have many Categories, and a Category has many Posts, so you need to do something like this . But I didn’t understand, is it necessary to create this object for each Post-Category pair separately and save it instead of the Post Category? or how?