Digikey's site has an excellent but complex search tool. First you type "capacitor" and then you need to know which category, in this case "Ceramic Capacitors" is the one you want.
Picking the general category is by far the hardest part, since you might not know why general type you need. If you're not experienced, sometimes the only way is to just keep trying different types until you find the right one. By guessing, you'll eventually figure out is right because it offers the right ranges of specs and the pictures of the parts with the correct specs actually look like the thing you want. For these parts, trust me, "Ceramic Capacitors" is the category you want.
Then you get a wide (horizontal scroll on any normal screen) list of parameters, for 643,291 products! That's an overwhelming number, but the many options are all meant to help you narrow this list down to just the parts you want.
The first step is to click the "In Stock" box and then "Apply Filters". Today that cuts it down to only 84,409 products.
Repeat this for everything you know. For example on that first part, you know it's 0.1uF. Find the "Capacitance" list and scroll down until you find 0.1uF. Click it, and again click "Apply Filters". Now (with today's inventory) that narrows things to only 3,012 products.
Filtering for X7R temp co trims the list to 1731, and clicking "0603 (1608 Metric)" narrows the list to only 71 products.
The only spec remaining (from the stuff I put on the list is 25V). With capacitors higher voltage rating is ok, since it's just a maximum before the cap might fail. The list goes up to 50V. If I click 25V, 35V and 50V and again "Apply Filters" the list is now 28 parts. Or if you didn't know this, just click 25V only and odds are good some will exactly match, even though using higher voltage rating would have been ok.
Many of them are "Digi-reel" which means you pay $7 extra to get them on a reel, which you probably don't need if you're building by hand. Maybe pick the cheapest from that list of 28, or look over the list and pick one at random. Any should work, since they fit all the listed requirements.
Repeat for each part. It's a bit tedious, but not difficult. Along the way you get to see what many of the buying options are. With a little google work on the choices, you can learn quite a lot about the parts. Or just follow this recipe to find parts that match the required specs.
If you need more options, maybe read up on what those 3 letter temp co specs mean. Just beware of any that begin with "Y" (meaning a low quality part) or "Z" (meaning a very low quality part - only meant for disposable stuff). Never buy those unless you're sure the low quality is ok for your needs. When the spec begins with "X" you usually have some flexibility when the board won't be used over a wide temperature range. If the spec if NP0 or C0G (meaning the same thing... apparently NP0 is someone's trademark or something) then do not buy a lower quality part.
There are tons of these little details, but hopefully the process of finding the right category and then narrowing the enormous list to just the parts that match the specs you need is at least understandable. With more knowledge and experience you can find more parts that are acceptable substitutes (like a wider temperature range), but even without that, generally you can use Digikey's excellent search to find a part with the exact same specs.
Hope this helps?
