aivest will only suggest a portfolio, i.e. certain amounts of certain stocks, that you may then actually buy through your broker.
You only have to enter a target amount and the currency you would like to use. The target amount does not include transaction costs, i.e. when you enter "5000 USD" as a target amount, then a portfolio worth about 5000 USD will be constructed by the optimizer. However, since you need to pay fees to brokers, exchanges etc. to order stocks, your total investment will be higher. Internally, aivest will use average transaction costs for the optimization, which cannot currently be customized.
Once you entered the necessary information, your portfolio will be queued for construction. Depending on system utilization this will take from minutes to days.