It's simple to invest your money into bitcoin. You just buy some bitcoin in exchanger which is in your country and save them for a long term. But its have high risk. I suggest you to do trading, after you buy some bitcoin. If you have big amount , you can do mining. Bitcoin is fluctuative digital money.
You might have confusion about the HODL and trade. You mentioned storing or saving bitcoin for long tiem and it has high risk. Thus you are suggesting trading.
trading is next level high risk activity one could do with bitcoin. If and only if you know how market is moving, what is happening in global market level and based on the analysis of these kind of things you deduce what might happen in future. And then you place your bets on bitcoin. This is trading. Few things are important to understand when it comes to get benefit from the bitcoin.
1. If you have less money for investment purpose, buy some satoshis or bitcoins as per situation and store it safe.
2. Repeat step 1 regularly
3. If you understand or able to predict what may happen in market then put some coins in trading
4. If step 3 is not feasible then step 2 is for you.
5. Keep your coins in your hardware wallet for long long time. You will be amazed after five to ten years realizing your saving value increased by bitcoin.