If you're using Shopify Payments, then the funds for your orders will be paid out to you within 2-5 business days (the length of time depends on the region, and can be seen here). Funds can not be automatically directed to your supplier once the purchase is made. If you're just starting out, and hope to fulfill the orders immediately, then you would need to front the costs of the orders to purchase the products. Alternatively, you can wait for the funds to be deposited before fulfilling the orders.
If you're not using Shopify Payments, then we would not handle the funds for your order. You'll need to contact support for the payment provider you have enabled in Settings/Payment Providers to determine where the funds are being deposited.