In a solo win boost the booster logs into your account and plays the ranked matches while you take a break. It is the quickest way to receive your wins, because the booster can queue whenever the lobbies are good without waiting for your schedule. Most customers who need a handful of wins before the end of an act, or who simply have no time to play this week, choose solo.
In a duo win boost you play every match yourself with a high-ranked booster in your party. The account never leaves your hands, the wins are games you actually took part in and you get to watch how a much stronger player positions, uses utility and calls rounds. It usually takes a little longer, because two schedules have to line up and the game limits how far apart the ranks in a party may be.
Before you post the request, make sure the account has reached level 20 and has finished its placement matches for the current act, and write down the exact tier you are in now. Choose how many wins you want, decide between solo and duo and add anything the booster should know: agents you want played or avoided, hours when you need the account yourself and your region, so the offers you receive fit your servers.
After accepting an offer, keep an eye on the chat for the first few minutes, especially on the first login, when an extra verification code may be needed. From then on the order runs by itself, its status is always visible on the order page and the booster keeps you updated in the chat. When the last ordered win is in, the booster marks the order as finished, you confirm the result and you can change your password and keep playing with the momentum those wins gave you.