As a heir to my mom’s estate how do I proceed?

If she had a will naming you as her executor, you have to go to the county probate court (county in which she lived) and have that appointment confirmed by the court so you have the power as executor. (If there is a will and you are not appointed by it as executor, then whomever was appointed by the will needs to do this.) If there was no will, you have to still go to the court, but request that you be appointed as the "administrator" or "personal representative" (different states use different terms) of the estate--this is essentially the same role as executor, but is court chosen and appointed, not named by the deceased in her will. If you are one of her children, then so long as one of your siblings doesn't oppose you for this role, the court should almost certainly appoint you and give you legal documents confirming your power and authority. 
Getting an executor or administrator/personal representative appointed is always step one, because only that person has power over estate estates: e.g. the power to put money from the deceased's bank account into an "estate account" to use to pay estate debts and later distribute to heirs; the power to otherwise collect assets and give them to whomever gets them (or sell them for the money); etc. The executor or administrator/personal representative also has the responsibility to pay debts of the estates (like any claims made by creditors of your mother against the estate). 
In terms of distributing assets, you have to follow the terms of the will if there is, or the rules for "intestate succession" (who gets what when there is no will) in your state. Ordinarily, her husband would get much, possibly all, of the estate, but the law doesn't let someone murder someone else and profit by their death, so you can oppose him getting his normal spousal share in court.
There are various procedural steps and forms you will have to follow or fill out, but it all starts with someone (e.g. you) being given the power by the court to manager the estate assets. 
Here's a link to a webpage put out by your court system with probate instructions and forms, to give you a starting point: https://www.courts.state.co.us/Forms/Forms_List.cfm?Form_Type_ID=143