Create a Claim
To create a new claim, place down a claim flag anywhere you would like to start. You must be further than 10 chunks from another claimed chunk, this is to prevent players surrounding another claim and boxing them in. The flag will stay for a couple of seconds, marking the area with particles that you have just claimed. Now that a claim has been created, it will show up in the RMT menu so that you can manage your claim.
You can expand your claim by placing a claim flag either next to your current claim chunks, or if you would like to start another group in the same dimension, you can place the flag over 10 chunks away from any current claims, then continue to expand as normal. Although these groups of chunks are not connected, they are in the same dimension, so follow the main claim settings unless added to a subclaim.