All you need is a non custodial wallet, money and exchange.
In short, you just need to send your money to the exchange/someone you trade, then you will get your Bitcoin in your exchange (if you trade using CEX) or wallet (if you trade P2P), if you use CEX you need to move your coins to your wallet.
I will like to explain that it goes in 2 ways, first, you can either buy BTC bit by bit (i.e either weekly, monthly or quarterly) and left for 'x' period of years, while secondly, you can buy once with a huge sum and left to grow, or lastly, you can equally work on a signature campaign on the forum and get paid in Bitcoin as reward.
You're talking about DCA and it doesn't need to left for the next few years because you can keep DCA-ing until you death.
Don't treat signature campaign is a job in this forum, it's just a bonus and not everyone join in this forum only for participate a signature campaign, @OP is still a newbie too and he have no way to participate signature campaign.