Individual retirement accounts are not a team effort. You can't add your wife to your IRA the way you can add her name to the title of your house. Even if you open an IRA after your marriage, you can't become joint owners of one account. There are, however, ways to give your wife a share of your IRA investing.
The one place you can add your wife's name to your IRA is on the beneficiary form. If you name her as your beneficiary, she inherits the account assets when you die, and without the account passing through probate. This doesn't give her any control or claim on the account while you're alive. If you live in a community property state, you may need your spouse's approval to name someone else as beneficiary.
If your wife is the only beneficiary of your account, she can do things no other beneficiary can. Non-spouse beneficiaries have to transfer the money from your account to a separate account set up to handle it, then start making withdrawals. Your wife, on the other hand, has more options: she can take over your account after your death as if it were her own, adding money to it and not making withdrawals until her own retirement. Depending on her age, of course, this often lets the money grow tax-free for years longer than if she were a non-spouse beneficiary.
Your spouse can't share your IRA, but you can pay for an IRA of her own. As of 2013, the maximum IRA contribution per year is $5,500, or $6,500 if you're 50 or older. If you earn less than that, you can only contribute as much as you earn. If your spouse doesn't earn enough to fund her own IRA, you can contribute for her. For example, if she earns nothing and you earn more than $11,000, you can deposit $5,500 in two IRAs, one for each of you.
If you put your spouse down as beneficiary, depending on your state's laws, divorce may not change that. Your account administrator's job isn't to decide who deserves to inherit your IRA -- it's simply to give the proceeds to your named beneficiary. Depending on where you live, if your ex-wife's name is written down as the beneficiary, your account may go to her. To avoid any confusion later, it's wise to keep your named beneficiaries up to date.