Every state places all of its laws on its own website, indexed by topic.
Do a little easy research, and have fun finding the answer to your question.
You will be amazed at all of the useful stuff you'll learn in the process.

While you're at it, you might also look at the applicable federal laws.
For that, try the BATFE's website.

As Steve said each State has it's own firearm laws so you will need to check with State and Local laws in Oregon. Here in TX I would not need to do anything except buy some ammo for it.

here in oregon you need not do anything.... there is no state mandated registration. just enjoy your gun