The best way is to be with an outsider when your partner is not in the town.
Or you can share it with a few close and trustworthy friends or family members.
Advertising your relationship status to everyone would not be suitable.
More and more couples these days are opting for non-monogamous relationship. In such relationships, two partners are committed to each other but at the same time, they are free to have physical relations with any other person, which he/she finds attractive.
It's almost impossible to you to not feel attached or jealous sometimes, so live this way , it requires you to follow certain open relationship rules. In most of the cases, infatuation makes people decide to be in an open relationship instantly.
For something that daring, you should respect him/her.
Before you go on with this relationship, make things clear between you two.
There might be things related to sex that are off the table.
So, it’s better to discuss them openly to keep your relationship smooth and steady.
For example, if you are a bisexual, make sure that your partner knows it and has granted you permission to be with both genders.
Or set a time frame for meeting with others be it weekly, monthly or in a fortnight. This is not one of those conventional open relationship rules, but still this is something you must do.
What the other one is thinking or doing should never be your concern.