How do I purchase ? How do I add to mt4

 
I’m very good with tech usually I’m a millennial and I can’t figure out how to actually purchase a product on here. I also have no clue how to login using meta trader 4 or 5. I’m looking all over.  I’m trying. To spend money but cannot. How do I do this ? 
 

read post (screenshots) about what to check, and the following information about where/how to find already purchased product (purchased by you):

Where can I see my purchases? 
https://www.mql5.com/en/forum/9950/page70#comment_2564931  

How to Install an Earlier Purchased Application
https://www.metatrader5.com/en/terminal/help/market/market_buy