Generally speaking, there are many solutions. What you need to keep in mind is that the easy to use ones are mostly easy to bypass, the hard to use ones are also harder to bypass. In my case, I use BitLocker as its virtually uncrackable as of now, and it's the right balance between ease of use and security. On top is part of Windows 10 (and 8 and 7) and so I don't need to have additional software in order to work on other PCs or in case I need to reformat my PC or buy/use a new one.
You can either set a portion of your disk as a partition and encrypt the entire drive, with BitLocker, use an external drive/usb stick, or use a VHD(x) virtual drive approach. I like the VHDx better as I can work on many PCs at the same time by having the VHD on an external drive and also can upload it to a cloud service. Sadly Bitlocker doesn't support individual folders.
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If you are just looking to encrypt few files, a quick solution would be to use RAR (not zip etc, those use weaker encryption), set a difficult password and it will be virtually uncrackable and fast but if you want to update it often or store many files it will get bothersome.
I almost always suggest those tools cause there are common and easy to find. There are more specialized tools if you want to go down that path but you need to also have them with you if you plan to use files on other PCs.
I'm sure others will propose other solutions so choose the ones that meet your needs. Google will be your friend too.
Hope it helped.