How do I plug this in?!?!

You will see it says Input: 100-240V. This means it can take any voltage between 100V - 240V.

Again it says 100-240V.

You will find some VERY hard to read. (and are located in silly spots!)  I have found sometimes taking a clear photo and expanding helps. And I have even gone back to childhood days to create a rubbing, which is easier to read!  

You can barely see on the rubbing, this item is 120V.

You will see it says 50/60Hz

Again it says 50/60Hz

This one only says 60Hz

High wattage devices (such as a hair dryer or heating pad) MAY need a voltage converter that has a wattage rating greater than the wattage rating of that device. High-wattage devices will use 1200W or more.

If a converter or transformer is described as a "dual-watt" accessory, it will probably handle the load, though you should double-check its high wattage setting to be sure.  

You can see in Pic 1 the Wattage is 10W, Pic 2 15W, Pic 3 is 177W (none are high wattage)

Preform an internet search for “Outlet plugs for destination country” 

For example I searched "Outlet plugs for Iceland".  One website that came up was https://iceland.nordicvisitor.com/travel-guide/information/electricity/   Here I was shown that it is a Plug Type "C" or "F", which is typical for many European countries (Picture 1 below).  This is a standard Europlug socket with two round prongs 

When I search "Outlet plugs for Ireland".  The first sites did not to appear to be from Ireland.  In this case I look at multiple sites that seem more technical.

1st - Electricalsafetyfirst.org.uk

2nd - Power Plugs & Sockets of the World

3rd - International Electrotechnical Commission

All three sites confirmed Ireland uses Plug type "G" which a plug that has three rectangular pins in a triangular pattern (Picture 2 below in aqua color). 

Electricity supplies worldwide can vary from anything between 100V and 240V. It can be extremely dangerous to use an electrical device that is rated at a voltage different from the supply.

With each search above, in the description it also stated the Voltage and Hz that country uses.

"For Iceland there are two associated plug types, C and F. Plug type C is the plug which has two round pins and plug type F is the plug which has two round pins, with two earth clips on the side. Iceland operates on a 230V supply voltage and 50Hz." 

"For Ireland the associated plug type is G, which is the plug that has three rectangular pins in a triangular pattern. Ireland operates on a 230V supply voltage and 50Hz."

If the destination outlets do not match your device prongs, you need an ELECTRICAL ADAPTER, which is a device that simply allows you to plug any US electrical device into a foreign electrical socket.  It is important to note adapters do NOT convert the voltage or frequency.  

If the destination voltage or frequency are different than what your device needs, a voltage converter (aka Converter) will be needed.   Sometimes you can find a converter and adapter in 1, they often cost more but is just 1 device rather than 2.  If your device was rated duel voltage (or says 100V-240V) then you will not need a converter. (this is also where you look for wattage converting if needed)

On Amazon I was given a list of multiple options, upon closer inspection, the first (least expensive) option was simply an adapter. "Type G Power Adapter" (this would only be good for devices that operate on the same voltage as the country uses.)  The second option was a "Type G Travel Convertor", this will convert voltage 

For plugging in multiple devices you can buy a single adapter plug and a power strip with multiple outlets. Though it's bulkier and pricier, a multi-outlet surge protector is even better, because it adds a level of protection for places with less stable electrical grids. (see pic 4 below - the top option is just an adapter, the higher priced one is also a voltage converter)