With an IRA inherited from a spouse, you have at least two options. @dmertz will remind me if I missed a third option.
A. Treat it as your own IRA. You can rollover the funds (combine) them into any IRA you own, or keep it as a separate account, but transfer into your name. You can withdraw money at any time for any reason, and pay the income tax. If you are older than your RMD beginning age, you must withdraw at least the RMD amount, but you can withdraw more if you want to.
B. Keep it as an inherited IRA (the account is titled something like "John Smith as beneficiary of Mary Smith."). It stays separate from your own retirement funds. You can withdraw money at any time for any reason, and pay the income tax. If your wife was older than her RMD beginning age, you must take RMDs based on your own life expectancy table (you can withdraw more if you want, but you must withdraw at least the minimum amount). You must also spend out and close the IRA by the end of the 10th year after your spouse died.