1 - From the Board View
When a participant connects to a Board, he / she has to click on the idea they want to "like" and then click on the "heart".
2 - From the List View
All he has to do is click on the "Board View" button at the bottom right of his Board and then choose the "List View".
Once the List view is displayed, he will be able to "like/like" several ideas quickly.
If you want to go further than the option proposed above, we invite you to consult this Article: Ask a Question on Board