has many through association rails - ruby-on-rails

Question

Users can upload tracks and create playlist. I have a model for playlist and i have a model for playlist_track which is for users that can save to the playlist. I can create a new playlist but how do i add the tracks to the playlist in the views?
ActiveRecord::Schema.define(version: 2018_12_06_050857) do
# These are extensions that must be enabled in order to support this database
enable_extension "plpgsql"
create_table "active_storage_attachments", force: :cascade do |t|
t.string "name", null: false
t.string "record_type", null: false
t.bigint "record_id", null: false
t.bigint "blob_id", null: false
t.datetime "created_at", null: false
t.index ["blob_id"], name: "index_active_storage_attachments_on_blob_id"
t.index ["record_type", "record_id", "name", "blob_id"], name: "index_active_storage_attachments_uniqueness", unique: true
end
create_table "active_storage_blobs", force: :cascade do |t|
t.string "key", null: false
t.string "filename", null: false
t.string "content_type"
t.text "metadata"
t.bigint "byte_size", null: false
t.string "checksum", null: false
t.datetime "created_at", null: false
t.index ["key"], name: "index_active_storage_blobs_on_key", unique: true
end
create_table "playlist_tracks", force: :cascade do |t|
t.integer "playlist_id"
t.integer "track_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "playlists", force: :cascade do |t|
t.string "title"
t.integer "user_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "plays", force: :cascade do |t|
t.integer "user_id"
t.integer "track_id"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
end
create_table "tracks", force: :cascade do |t|
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "genre"
t.integer "user_id"
t.string "name"
t.date "release_date"
end
create_table "users", force: :cascade do |t|
t.string "email", default: "", null: false
t.string "encrypted_password", default: "", null: false
t.string "reset_password_token"
t.datetime "reset_password_sent_at"
t.datetime "remember_created_at"
t.datetime "created_at", null: false
t.datetime "updated_at", null: false
t.string "username"
t.index ["email"], name: "index_users_on_email", unique: true
t.index ["reset_password_token"], name: "index_users_on_reset_password_token", unique: true
end
add_foreign_key "active_storage_attachments", "active_storage_blobs", column: "blob_id"
end
Here is my track model
class Track < ApplicationRecord
has_many_attached :mp3
belongs_to :user, optional: true
has_many :playlist_tracks
has_many :playlists, through: :playlist_tracks
has_many :plays
end
and here is my playist_track model
class PlaylistTrack < ApplicationRecord
belongs_to :playlist
belongs_to :track
end