There two things you need to do to edit the wiki: edit and merge. First, click the blue pencil at the bottom right to start editing.
Be sure to track any changes you are making using the Drafts box in the left panel.
Then, click Merge in the left panel to submit your changes. This is an extremely important step. Without merging, the wiki won't update with your changes.
You can check if the wiki updated by visiting the wiki website: https://childlanglab.gitbook.io/childlanglab-wiki/