Yes. To do this, log in to myAlpari, "My Accounts" – "My Trading Accounts". Choose your account and the amount of leverage you would like.
But should you lower your leverage? Let's say you have 10,000 USD on your account.
With 1:100 leverage, it will take you 1,000 USD to open a 1-lot position (10% of your funds). A Stop Out will be triggered when your losses reach 9,800 USD. For EURUSD, this is more than 980 pips.
You need 3,000 USD (33% of your funds) to open a 1-lot position with 1:33 leverage. A Stop Out will be triggered when your losses reach 9,400 USD. For EURUSD, that is more than 940 pips.
As you can see, lowering your leverage will subject you to stricter margin requirements. If you are looking to minimize your level of risk, we would encourage you to instead look into the rules of proper money management.