You’ll really need to re-post with some actual detail, this is all a bit vague at the moment.
What do you mean by launch button (no such creature as far as I’m aware)?
If you are talking about having downloaded BP then you need to unzip the package into your plugins folder and then log in to your WP site and activate said plugin. If you are talking about having run the auto plugin install of BP then similar idea; with it now living in your plugins section of WP it needs to be activated and a suitable BP theme selected. If you’re talking about WP itself then follow the 5 min install guide on the WP site