How do I install my cartridge?

I recently bought a Denon DL-110 and a used Denon DP-300F that didn't come with a cartridge. I have no idea where to install the cartridge, and how to do it. The cartridge isn't coming out of the glass "thing" it's attached to....and I don't have a screwdriver. Do I need one?
Sorry if this is a stupid question, I'm just new at this, haha.
It may be worth it to employ the services of your local stereo dealer, at least if you don't have a knowledgeable buddy.

Having say that, some basic tools and the instructions go a long way. YouTube features videos on cartridge mounting. You may wish to seek help from fellow member who live in your area.
... and I don't have a screwdriver. Do I need one?

Normally yes.
But it is possible that yours is Sirius compatible, did you try to give an order via iPhone4s: "Mount yourself"?
Glen makes some great points. I definitely recommend getting someone more experienced to show you the ropes.

Another invaluable tool is - they have alignment protractors that you can print out and tons of advice. Just make sure that you pay attention to the scale instructions if you use their protractors. It's a great free resource.
In most cases, properly installing a cartridge requires at least a little knowledge and ability. If you don't have a screwdriver, don't know where to mount it, and can't get it off the glass thingy I think you may be miles away from doing a proper job.
Have someone do it for you.
The most frequent accidents in installing a cartridge is tearing off the clip on the end of the arm wire. This is because people try to put the clip onto the installed cartridge pin with a pair of slips, and off comes the clip. I have found that it will not happen if you wire the cartridge BEFORE installing it in the arm. Push the cartridge pins on to the proper colored wires by holding the cartridge in your left hand and pusing the cartridge pins on to the wires and then attaching the cartridge to the headshell. Zei Gazundt.
vewy, vewy carefully.

No screwdriver? To really do it right, you also need an alignment gauge, a cartridge scale, and a Fozgometer. That is almost $450 worth of stuff, although someone with lots of experience may be able to do it with less. The bare minimum would be a DB Systems protractor and a Shure mechanical scale (about $80, together.) In your case, there is no doubt that you should find someone to do it for you who has the tools and knowledge.

The glass thing is there to protect the cantilever from you. It should pull off easily, but you have to pull in the right direction.
Might be a stupid question, but is there a website that I can ship my equipment to and pay them around 30 dollars to have them install and align my cartridge and ship it back?
Where do you live? Maybe someone can recommend a dealer.
read this an do it yourself. You will have a much better analog experience learning how to do it yourself versus someone else installing.
You wont even be able to ship it for $30 much less get it repaired and shipped back. Find someone local to do this for you, pay attention and learn.

Or buy Michael Fremer's DVD on how to set up your turntable. It is available at a number of on line vinyl retailers for about $30. follow his instructions and you should be ok.
I live around LA. and thanks, I'll check that link out!