You need to set you radio program to use the computer port your using. After you set the port, have the cable connected to the radio. Then connect the cable to the computer. Wait until the computer senses the cable. If your speakers are on and you have it set to make a tone when it connects, you will the tone. Then you can continue to read the radio.
There are a number of different versions of the radio. Which one you need will depend on which version was last used. You can't use a lower version, but the same or a higher version will work.
You might want to check with your source of the radio. It will be an Astro 25 version software you need to use.
I always use the mic connector programming cable. That way if it is a remote mount already in a vehicle, I don't have to dig to get at the radio.
If this is the first time trying to use the programming software for this radio, you need to read about how to use the software. There are a number of different places in the software you will need to go to to do any frequencies changes.
I have 4 of these mobile radios set up on ham frequencies. I have set up zones to cover different locations. I have set up scan for each zone. I have set up direct talk around for each channel (mode in Motorola language). Plus the PL tones needed for both receive and transmit. Don't forget that some repeaters don't send out a PL tone, so those will have to be set as carrier squelch mode.
You can see this is a convoluted number of steps you need to go through.
Before I even start to program one of these radios, I always put down on paper, just what each channel (mode) will need to be set in the radio. It saves a bunch of frustration when the radio doesn't operate correctly.
Plus finding the different places you need to go is always a major challenge. Even working with these model radios, I still have to fumble around in the RSS software to find the spot I need to go to for each step of the programming.
Another point I need to point out to you. If you need to set the radio up in zones, you can only have 15 channels per zone in the scan mode.
If you have only a few more than the 15 channels, you need to set up zones to handle the number over the 15 channels. This is why I say to try and group your channels by location. Maybe consider putting in the common simplex channel in each of your zones. This way if your on a zone that is not your home zone, you will still hear the simplex call.
This brings up 2 more topics. One is setting the home channels for each zone and also setting the home zone. This way when you power up the radio, it will always go to the home zone and home channel you want.
So happy programming. Don't expect to just walk through it, like a walk in the park the first few number of times. Depending on your memory and skills, it could go easy, or you will find yourself stumbling all along the way.
Jim