There's a lot to learn from those threads listed above.
My first and foremost advice is to be patient and accepting of each others different needs.
Being mono means that you love one person romantically at a time.
Being poly means that you can love more than one person romantically at a time.
What mono does not mean is that you get to tell the other person THEY only love one person at a time.
What poly does not mean is that you get to tell the other person THEY love more than one person at a time.
Relationship negotiations require that both partners have the freedom to express their needs (I find BDSM helpful here in using the idea of hard limits and soft limits).
If having your partner ONLY have you for a partner is a hard limit-you can't make a mono-poly dynamic work.
If having your partner have more than one partner is a hard limit-you can't make mono-poly dynamic work.
There has to be room for the other person to be DIFFERENT and have a different love style in order for compromise to be reached-so it has to be soft limits.
On the other hand-if having your bed NOT SHARED-is a hard limit-that is something one can compromise on within a dynamic-because one can still love multiple partners without dragging them in and out of each others personal bed..
Does that make sense?
It's been very helpful for us in understanding that each of us has needs (hard limits) and wants (soft limits). Needs are non-negotiable-so either we are all able to get them met with one another-or the relationship is a no-go. Wants are compromise-able.
"Love As Thou Wilt"