OK - the plan to separate and divorce is easy. The "need him to leave" - is not.
In general this is how divorce happens.
1.You file for divorce - can be done online.
2.You two agree on how you split finances and how child arrangements work in the future
3.Your agreement is sent to Court, Judge looks it over and approves - you get decree nisi
4.You divide assets, as per your agreement
5.After a bit of time, you ger Final Order - decree absolute - and you are divorced.
STEP 2 is, of course, the most difficult one. Can take forever, and is usually the most painful bit full of conflict.
Step 4 - is the time where partners actually move out to their new place of residence. Before that you have NO right to ask him to leave. Until then - you both have an equal right to your marital home.
As to where YOU start - depends on your personal situation. Do you work? Do you two own your house? Do you have savings? Will you be able to support yourself after divorce, would you be applying for child support? Would you be able to buy/rent a property? Will you need legal representation - can you afford it?
Be prepared - separating/divorcing is not a quick process. If he is controlling now - he'll most likely put up a fight and make it all difficult. You need to arm yourself and be strong. He'll turn into an even worse version of himself and make your life even harder - but in the end it'll be worth it.