A core tool in becoming a DIY Income Investor is to manage your portfolio online. Once you have progressed to Level 4 on the Income Pyramid you will need an online Broker to access your local stockmarket.
You should look for a 'no-frills' execution-only broker - one that doesn't offer advice or try to manage your investments. They should offer low share-dealing costs and annual maintenance charges. You won't be dealing often, so you'll need to make a judgement about the balance of costs - its the total annual cost that you need to focus on.
There are several possible providers in the UK: you could start your DIY research here and here. The Motley Fool has a discussion board on online brokers and share dealing which might help you to select one. All of them offer Stocks & Shares ISAs.
It is a pretty easy process to apply for a self-select ISA online. Typically your online ISA will be connected to your online bank account (hence the importance of having an on-line bank account) to allow transfers of cash to top up the ISA. D-I-Y finance. Easy - you just need to get started.
I use two different providers (to stay within the UK government's guarantee limits), which I have found to be effective and inexpensive: iDealing.com and TD Direct.
So, once you have your on-line self-select ISA topped up with cash - you're ready to go!
Then comes the hard part - what to invest your money in? Our recommendation is to start with an income-producing ETF.
I can't really help for the US from personal experience. However, here is a summary guide to US online brokers - and there are lots of other sources of information.
You will also need to consider whether or not you will be opening an IRA or Roth IRA with the Broker.
I am not a financial adviser and the information provided does not constitute financial advice. You should always do your own research on top of what you learn here to ensure that it's right for your specific circumstances.