Step 3: Claiming land
Land is done on a chunk basis, to see the chunk visualizer, press F3+G (or CMD+F3+G on Mac). You can claim as many chunks as your "Town Size: 1/X" shows in /t. You will already have 1 claimed as that is the home block.
To claim, stand in a chunk next to the one you've just claimed (your home block). You have to claim chunks that are already directly connected to your town unless you're making an outpost (a town claim away from your main town area, as explained in Step 4).
/t claim in the chunk you're in to claim it, and repeat this as many times as you like. If you unable to claim anymore and you have enough money in the town bank, you might have reached your Town Size limit. This can be increased by joining a nation, or by buying bonus plots with
/t buy bonus <amount>.