SMP uses a different, more simple, method for claiming your land. You will need claimblocks to be able to claim land, and claimblocks can be earned in many ways (these methods are listed below). Once you have a sufficient amount of claim blocks you will need a golden shovel to claim your land, simply right-click the two corners, diagonal to one another, and your land will be safe.
One claim block = one block of land
(i.e, to claim a 5x5 area, you will need 25 claim blocks)
[a full guide on how to work the land claim plugin]
Your land will be unclaimed after 60 days of inactivity if you've claimed less than 2,000 blocks!
How do I get claimblocks?
There are many ways in which you can collect claim blocks, such as:
Visiting Toby to exchange Tokens into claimblocks
Claim Block Pouches from Crates, Vote Party & Pinata Party
What other commands do I need to know?
/unclaim - abandons the claim you are standing in
/trust [player] - allows you to select certain players to be able to build/interact in your claim
/untrust [player] - removes a players permissions in your claim
/accesstrust [player] - allows you to give certain players access to: buttons, levers, and beds
/containertrust [player] - allows you to give certain players access to: buttons, levers, beds, crafting gear, containers, and animals
/trustlist - provides a list of all players who have permission in your claim
/claimexplosions - toggles if explosions will work in a claim