Receiving the signal
There is no fixed limit on how powerful a signal could be sent by a civilisation like ours. We use klystrons to send very powerful radio signals, with deep space communication being one application; the Wikipedia page mentions a 1MW klystron used at the Arecibo observatory.
For a simplified estimate, let's say your transmitter is a point source with power 1x108W (100MW). The signal expands in all directions, so by the time it reaches a receiver 5 light years (4.7x1016m) away, its power will be distributed over a surface area of 3.3x1034m2. This gives an intensity of 3x10-28 watts per square meter (Wm-2), which is extremely weak. However, if the transmitting civilisation knows where they're transmitting to, they don't need to broadcast in all directions. If they focus the signal into a 1-degree beam, that will increase the intensity at the target planet by a factor of about 100,000, giving 3x10-23Wm-2.
If your receiving civilisation has an antenna one square kilometer in area, it will therefore receive 3x10-17W of power. That's slightly more than a billionth of a billionth of one watt, which is very weak. But it's much stronger than the signals NASA receives from the Voyager space probes, for example.
Are computers required?
...However, NASA uses a lot of signal-processing tricks to isolate those very faint signals from the background noise, and these tricks pretty much require a digital signal. I believe you would need at least a 1970s level of computer technology to even detect the signal, and your listeners would have to figure out the coding techniques before they could look at the actual content.
Once that's done, because it's a digital signal, they'd see the message as a string of numbers. The numbers could be anything – prime numbers, text, a JPEG file – but I think if you wanted to send a message, the best bet would be an audio waveform, like you'd find on a CD.
Obviously, this will be a problem if the receiving civilisation doesn't have ears. But if they do, it's probably the easiest thing for them to figure out; if they've seen a sound wave before, they'll recognise what it is. Any kind of image or video would involve another layer of complexity and assumptions, and would require more advanced computers.
But as blind people know, you can communicate a lot with sound. Provided the receivers can get this far, they don't necessarily need computers to figure out the rest of the message. You could start by playing sounds that they'd likely understand – a metal bell, running water – and gradually build up a language from that. It'd be a painstaking exercise, but it's interesting to think about.
This one is no problem. They're hearing you through some kind of radio telescope, and they will certainly be able to figure out where you're broadcasting from. In fact, they won't hear you at all unless they're pointing their dishes in roughly the right direction...