Creatures you control gain only activated abilities of the exiled land cards. They don’t gain triggered abilities, static abilities, or keyword abilities that aren’t activated abilities.

Activated abilities contain a colon. They’re generally written “[Cost]: [Effect].” Some keywords are activated abilities; they have colons in their reminder text.

If an activated ability of a land card exiled with Steward of the Harvest references the card it’s printed on by name, treat the version of that ability on each creature you control as though it referenced the creature that has it by name instead.

Land cards with one or more basic land types have the intrinsic activated ability “{T}: Add [mana symbol],” even if the text box doesn’t actually contain that text or the card has no text box. For Plains, [mana symbol] is {W}; for Islands, {U}; for Swamps, {B}; for Mountains, {R}; and for Forests, {G}.