If you have a four-digit PIN, and have notified your bank(s), you are good to go. Here are some concise recommendations based on experience:
1. The WORST exchange rate is at your departure airport money exchange. They may not charge commissions, but they make it up with an unfavorable exchange rate...in their favor....not yours. So, do NOT change money before you get on the plane, at least at the airport.
You may choose to obtain some Euros from your local bank if they offer this service, before you depart. I have been told that can be cost-effective.
I do not do it, as I keep my Euros from previous trips...I make the trip two to four times annually. I always have a couple hundred Euros in my Euro wallet, ready to go.
2. The NEXT WORST exchange rate, although fractionally, is at airport ATMs. All banks know that most travelers make a bee-line for the first ATM they spot at the airport, on arrival. So, they shave the conversion rate, fractionally. It does not usually make a big difference with the traveler, as they NEED the cash. But, at the end of the day, the bank profits...hey they are banks. It is what they do.
3. The overall "best" exchange rate will be at an ATM mounted in an attached physical bank branch in a large town or city. The big Spanish banks include Santander, Sabadell, Banco Popular, and others you will come to recognize quickly.
4. For safety and security, AVOID USING FREE-STANDING ATM devices in gas stations, cafes, convenience stores, or other such places. The sole exception is a free-standing ATM that is plainly, clearly and obviously the property and responsibility of a major Spanish bank: Santander, Banco Popular, Sabadell, etc.
Like in North America and the rest of the world, ATM machines found in gas stations, hotels, retail stores, or convenience stores are frequently operated by a third party for their convenience and profit, not yours. Hence, they always charge "convenience fees" and always have a bad exchange rate. This is also the highest risk of having your card information skimmed and stolen.
As an example, I will use the ATMs located in SOME 7-Eleven convenience stores in the States, but ONLY because they are operated by Citibank, a world-wide banking firm. They are so labeled, and the software is clearly from Citibank. THAT is how you make a determination, before you stick your card into the slot...
It is like other things in life...pay attention...
So, BOTTOM LINE, when you arrive in Madrid, Paris, or wherever, take an initial €100 withdrawal at the airport (if needed) to give you enough funds to get away from the airport environment, and to your first night's lodging. Near that place, you will find a real bank, with a more agreeable ATM. Get enough Euros there to last you about four days.
You will get the rhythm of your out of pocket expenditures and recognize when it is time to top up your wallet. Initially, I usually plan on about €50 per day. Plus, I pay for EVERYTHING possible with cash. I only use my cards in the ATM, or a department store, supermarket, pharmacy, or train station ticket kiosk. I also stay in hostals, not albergues, so my daily spend is higher than most others. You might adopt a lower daily average, if you are comfortable with that. Everyone is different.
Also, try not to use credit or debit cards in places where the card is out of your immediate and direct control at all times. So, buying groceries in a supermarket, or supplies at a pharmacy, or in a shop, where you can use a debit or credit card at the register is okay. But, giving your card to a server who leaves your table to process the sale behind the bar is a "no-no." That is how my cards have been compromised three times in three different countries. If you do not have direct control of the card at all times, the card data can easily be stolen.
Do not be paranoid, just be observant, and PAY ATTENTION. After walking across northwestern Spain in the "boonies" for a week or more, coming into a large town or city can be jarring and very disorienting. You MUST remember to turn your street smarts back on.
I hope this helps.