Only Platinum members can claim a plot in the creative word, however you can invite anyone (including user) to build within your plot so long as you remain online!

For help with Plot commands visit: https://support.liveandbuild.net/membership/plot-commands/

To teleport to the creative world goto Spawn and find the “Warp Room”.
To return to the overworld simply use /spawn or /home (if set).
Once in the creative world you may use /sethome <name> to easily return at any time, from anywhere!