The result of the process that one would put the disk through when using fdisk, and later plan to make that disk a part of an LVM setup (and for the purpose of education/exam situations) is that disk/partition labeled as of type "8e Linux LVM". Once labeled that way, it is easy to plug that memory device in the existing LVM scheme.
So let's say you are creating a new partition on an existing disk- after pressing "p" or "e" to give the partition type to fdisk (primary or extended) and specifying the size of the new partition, press "t" and then write "8e" to make that partition type Linux LVM. Once you are done with any further changes, write those changes to disk and that's that with fdisk.
fdisk is an interactive utility, at any point you could access its help or list available options.