This depends on where you reside and what currency you want to transfer to USD
Australians - Transferring AUD to USD
You can fund your trading account at your funds page the following ways:
This goes directly to the US via OFX and is the fastest and cheapest way to fund.
There are no card fees when funding via POLi
Debit / credit card
Funds get sent directly to the US via OFX. Can fund up to $10,000. There is a 2% (min $1USD) fee on all card transfers and an additional 0.5% for express funding.
Fund AUD into your AUD Wallet (powered by Macquarie Bank)
If you fund your AUD wallet you will activate and receive a Macquarie Cash Management account. You can then transfer these funds into USD on your funding page.
The details of your AUD wallet are provided to you by email and in your FUNDING page on Stake and you can transfer funds here by EFT. Once your funds are in your AUD wallet you can transfer to USD on Stake to trade. This is all done on your ADD FUNDS page.
You can make a direct transfer from any currency into your trading account via your preferred FX remitter or bank.
Already have USD
This is pretty easy. See here for more details.