Learning English can be very difficult and often time boring. To make my classes more interesting so my students do not get bored I like to use a lot of TPR (Total Physical Response). For example, if the word they learn is "run" I will ask them to show me how they run. This gets them up and moving.
Another way I keep students engaged is by using props. Props are my best friend. They help not only teach the topic better but interest the student a lot more. Often times this leads to them showing me their props as well. For example, to teach the word "in" I put a toy "in" a bag. Sometimes the student will then go run and get a box or a bag and put something in it as well. They love showing me their props.
The last way I keep my students engaged is by playing games. Depending on the age of my student I will play games like tic tac toe and rock paper scissors. For tic tac toe I use a clip board and painters tape and write words in each of the places the "X" and "O"s go. Then the student says a word and that's where I place their X or O.
Online learning is tough but through these three tips I find that my students are a lot more engaged and aren't as bored!! Good luck!!