Question: My attendant and I met a year ago and had intercourse back then, we recently picked back up where we left off, but want to go about it the right way and get married.

Is there a time frame that we have to be apart from each other sexually and not sexual before marriage?

What is needed to be done for our marriage to be halal?

Answer: 
There's no time frame, but both of you must repent to Allah(SWT) and never commit that sin again.

You and your potential cannot be alone together privately anywhere and at anytime. 

You must restrain your looks at each other.

You must have a **Wali** involved to go about your business with him.

You must be covered properly i.e. hijab, and he must have himself covered properly also.

There can't be any intimate conversations between the two of you.

Until you're married, you can't really have much physical contact.
If i understood what you said i think you write this advice to the person who will get married
Yes that's right but i just add to your spaech or i can say in the other word ...... tray to don't do the sins than allah will help you ...
And even you didn't have contact physical before get married , you will found the happiness in your life because whoever fears Allah - He will make for him of his matter ease.
my greetings ... your sister maryam