First time with edibles, start low. Like 10mg. See where you are in ~3 hours and take a little more if you still aren't there. 10mg is fairly low for the vast majority, but should be easily noticeable to most inexperienced consumers while not likely to be too much to handle. The effects from edibles can very much sneak up on you and take a while to present. (Usually 1-2 hours but varies from person to person.) Peak effects after that tend to last ~4 hours followed by another few hours of comedown. Taking too much is very much unpleasant both physically, and mentally. We had to comfort our ex for like 4 hours once because she took too much and was not at all handling it well mentally and had a complete breakdown. We've also taken too much before to relieve pain and it physically feels awful to "green out".
We also recommend to not combine with a CTB attempt until experienced. THC can cause anxiety, especially if too much is consumed. Paradoxically, it can reduce anxiety in the right dose and if the effects don't cause you any discomfort. Too high of doses are very likely to cause severe anxiety.