If you are an administrator, you can create a Broadcast under Settings -> Account -> Configure broadcasts to send an important message to your team. Broadcasts are key messages or instructions that you want your users to read. They are presented account-wide at the top of every screen.
You can format the text, include an image, decide when to enable the message, and whether they are sticky (permanent until you disable them).
Here is an example of the type of message you might want to post:
"Welcome to Aha! I was recently introduced to this breakthrough product and am excited about what it can do for us. It's going to revolutionize how we set product strategy and manage our roadmaps. As your administrator, I am thrilled to add you and the other core product team members to this account. Starting immediately, all product strategy, releases, and user stories will be generated, updated, and stored here. If you have any questions, please contact me at firstname.lastname@example.org"