1. Open overseas brokerage.
Preferably interactive broker. Keep in mind there's an inactivity fees of USD10/month if you don't have usd100k in cash or portfolio worth or unable to generate usd10 worth of trading commission.
2. Fund the brokerage.
3. Once money is inside brokerage, you can start buying.

How much to put in each time depending on
1) how much money you have
2) how much are you willing to put in

How often to put in depending on
1) how much money you have

Kindly Google arkk price. For real price use investing.com or MarketWatch. Current price is usd141.

For us stocks you can just buy one share. Aka only pay USD141. If you use pure interactive broker (the one with usd10/month charges) you can buy in fractional shares. Means you don't need to buy 1 share. You can even buy 0.01 share of it = usd1.41 but you still pay same commision of usd0.35/transaction.