How can I configure my flask server running on Heroku with static ip

I want to run my flask server with static IP's because Bybit needs static IP's for there API.

I have connected fixie extension to my Heroku app but I do not know how to configure the proxy or what I have to do so when I send a request to Bybit I have a static IP.

Here is the flask server:

import config
from pybit import usdt_perpetual
from flask import Flask, request

app = Flask(__name__)

@app.route('/execute_trades', methods=['POST'])
def webhook():
    exchange = usdt_perpetual.HTTP(
    endpoint="https://api.bybit.com",
    )

    last_price = exchange.public_trading_records(symbol=symbol,limit=1)
    
    return last_price

Here is my Procfile:

web: gunicorn server:app