There are many different ways that you can introduce
a new structure to your students.
You can talk about a known subject using the target structure.
Then check students' understanding by using simple questions.
You can do a simple drawing on the board and talk about
it using the target structure.
You might talk about props or classroom objects using
the target structure.
You could also write example sentences on the board,
and help students work out the rule by looking at the examples.
If you like, you can bring in an English newspaper headline,
advertisement, or other simple piece of writing containing the target structure
and show it to students. Copy the example on the board and help students work
out the meaning.