- a computer that is always on (old laptop, whatever)
- an internet connection that doesn't have overage charges
- ~10g of free hard drive space, though 200g is ideal
- a Windows, MacOS, or Linux operating system
You probabally want one of these three:
For Windows or OSX, just install it in the usual way. With the Linux version, you can just untar it in your home directory, and run it directly from there. The thing you want to run is called bitcoin-qt, which is the graphical frontend of the bitcoin full node.
The first time you run it, it may ask you where you want your data directory. If you happen to have 200g of space laying around, maybe on another partition, that's great. If not, click through the space warning anyway, and in the next step I'll show you how to run a bitcoin full node with drastically less hard drive space.
The "prune" setting in bitcoin.conf is measured in megabytes, so if you say "prune=10000", that means use 10 gigs for storing the blockchain. If you say "prune=5000", that means your node will use 5 gigs. Please donate whatever space you can, and remember, you can always make this number bigger or smaller later. In the following example, I'm going to start with 10 gigs.
To set your pruning setting, go into the menu, and do:
Settings > Options > Open Configuration File > [ OK ]
add the line "prune=10000"
Save the file and quit. You're also going to want to exit and restart the bitcoin-qt app. Congratulations! You are now helping to run the most powerful payment network known to man.