You probably can't.
Consider the last time someone tried to "make" you do something you were uncomfortable with doing. How did that make you feel? Even if the experience didn't turn out to be that bad, did the focus on making you amicable towards it assist with the process?
"If this is really what you want to do, I guess it's okay. You're not giving me much of an option."
Why do you need to make your partner "okay" with you dating other people? This does not mean you should cheat on them; it simply means why do you think this is something they have to be okay with? They may never be okay with it, no matter how you paint it - so then what? If your partner is open to you dating other people, all you can do is offer education on polyamory and transparent communication during the dating process. This does not translate to "making them okay with it." It is essential to understand that you cannot make someone "okay" with something.
out of obligation and love
Framing yourself dating other people as something your partner HAS to be okay with will create an ultimatum situation, even if this is not your intention. Your partner may attempt to be comfortable with this simply out of obligation and love for you. Down the line, this will fester into resentment. Also, when you are trying to "make" someone be amicable towards something, there is a thin line between good intentions and manipulation. It would be best if you did not try to manipulate your partner into experiencing a feeling that is not their own. If someone is not okay with something, it doesn't mean they will be against it.
I'm okay with you dating other people, so you should be okay with these rules. Don't forget that.
You do not want your partner's acceptance of you dating other people to be transactional. "If I'm okay with you dating other people, you have to be okay with insert restriction." It would behoove you to unpack why you need to MAKE your partner okay with something, therefore removing their emotional autonomy.