Q: I'm trying to connect my iPad to my HP Laserjet P1102w so I can print. How do I do it?

I don't see the HP printer on the list here. About AirPrint - Apple Support

You would need it to be on the list and connected to your network via Wi-Fi. You would have to be on that same Wi-Fi network. However, there is an HP printing app that you might also be able to use if the printer is not on the list of AirPrint printers. Do a search of the App Store to check on the compatibility of the app and printer.

The Printer Manual offers an airPrint section, but does not say whether every model of the 1100 series supports AirPrint or not

http://h10032.www1.hp.com/ctg/Manual/c01695231

Assuming it does, you need to connect your printer to the same wireless network your iPad is connected to.

Once that is done, you will need to find the action icon ()in any App you want to print from, and then tap on the Print option.  Then you can tap on "Select Printer", and wait for the iPad to find the Printer. Once it does you can select it, and print to it.

Print from your iPhone, iPad, or iPod touch - Apple Support

If you are not seeing the icon, it makes me believe the device does not support AirPrint. You could contact HP and question them, and ask if there is a firmware update for the printer as well. You say the devices are connected to the same server, I'm not exactly sure if you are referring to the fact they are all on the same Wi-Fi network. The printer has to be connected via Wi-Fi to work correctly, and the iOS devices need to be connected to that same Wi-Fi network.

Not sure what you mean by "My iPad iPhone and computer are linked to the same server."

What is the Printer connected to? and how?

I agree with Chris, in that you may need to contact HP to determine if your specific model supports AirPrint.  Your iPad and iPhone require and AirPrint compatible printer to be able to print to it, your computer does not.

If you are using the Gmail App, then you can only print using  Google's Cloud Print, and not AirPrint. There is no option to AirPrint from within the Gmail App as that is how google designed their App. The Print option can be found in the  ^v menu option at the top of the screen where it will request you setup your printer with Google Cloud Print.

http://www.google.com/cloudprint/learn/

I would suggest you setup your Gmail account in the default Mail App instead to make Printing emails easier.

http://www.imore.com/how-to-setup-gmail-google-calendar-contacts-iphone-ipad

Ah, that tells us a lot. It would have helped earlier, but at least you got your answer. I'll have to add that printer to my list of those that works but is not listed.