Below is a short video with some tips on how to take a motif
“Motif: a short succession of notes producing a single impression; a brief melodic or rhythmic formula out of which longer passages are developed”
… and make a few simple changes to expand it into a verse or chorus. The idea expressed in this video is to come up with a small melody idea and be able to repeat it 3 times but each time changing it just enough to keep it interesting. This strikes a good balance between something familiar for your listener while at the same time, providing something new with minimal effort.
There are many methods for altering a motif that I won’t list here, but this video shows 2 examples that should be easy to re-use in your own composing efforts.