Agreeing with everything Emma has said!
Since she's so young there's no hurry to get to 3 meals. I would start with either breakfast OR lunch (whichever suits you and her the best), and go with that for a few weeks before introducing a second meal. There is no rush at 4mos to get moving quickly with solids, and since milk will still be more important for her nutrition than solids, you want to make sure she is still drinking all her milk and not decreasing the amounts in favor of solids.
It's best to give solids about 1hr after her milk feeds, so you could either do it at 8am or 12pm. Pick a time when she is happy and well rested. She will not be as keen to try something new if she is tired.
And definitely leave a lot of time to watch for a reaction. I've read to leave at least 4 or 5hrs before bedtime after trying new foods, but even more time is probably a good idea.
The most important thing, follow your baby! If she takes to solids like a duck to water, then you can proceed a little faster. But if she is hesitant to try it and doesn't seem ready, don't feel like you have to push. You can always give it a break and try again at a later time.
