You will be put to the test of your Saiyan will in the Welcome to Frieza Force Bonus Battle against a slew of powerful enemies. It is quite far from an easy task as you have only Nappa by your side. There have also been some restrictions that make the battle all the more challenging.
If you need help with the quest, here's how to complete it: Welcome to the guide on Dragon Ball: Sparking Zero's Frieza Force.
There are a couple of unwritten rules concerning Sparking Zero's Welcome to Frieza Force, which you will not find on the official page. If you check its 'View Effects' part, there are lots of limitations that can make you fail. From this task description, you can't fight Frieza with an Emote or an ultimate attack.
Any of these actions will have you lose the fight and allow Frieza to use his finishing move on Nappa. You cannot use the ultimate attack, Nappa Cannon, on Frieza because he will take that as a disrespectful move towards him. You still can use it on other characters, though.
Defeat Frieza Force Soldier, Cui, Dodoria, Zarbon, and Frieza 1st Form in that order when the battle starts. Once one character dies, his spot is taken by who's next in line behind him. Since Frieza Force Soldier is the first to fight, he shouldn't be as hard compared to the rest of them.
You will be applying a blind to the enemies for every switch of character. This de-buff is shown as an icon in the top left corner with a cross over it. You'll have to observe your surroundings closely in order to re-position your target.
This fight is way more challenging compared with the previous two because his nearly impenetrable guard makes it; counter this with a few unexpected hits using Instant Transmission or Z Burst Dash. That would be when things start to get hot, and the involvement of Zarbon comes into place. If you want to save your health, better avoid his special attack. Keep in mind that you only have Nappa as a weapon in this case.
Fast beat up all opponents using the Saiyan Spirit ability in tandem with Sparking Mode's Rush Attacks, common punches. Sparking Mode is an especial form where you will be able to charge up your Ki for temp-buffed bonuses. Throw your opponent with a bundle of blows so he will come down asap. You can use this mode effectively with Frieza, too, though be sure not to unleash Nappa Cannon, since it will result in instant loss.
Along with increasing your power, Saiyan Spirit gives a huge boost to your character's strength. Since you'll be facing the most powerful contestant, I feel that Frieza's battle is an excellent place to use it. Even his weakest 1st Form can be quite a nuisance to handle when your health is really low. Fortunately, when Nappa's health falls below a certain level, there are two beneficial bonuses in the Bonus Battle. Once his bar drops to 50% or 25%, his bar automatically fills in Sparking Mode. Now is your opportunity to hit some moves without you having to charge up your Ki.
The quest continues further, and with each character switch, different bonuses are received, such as the Rush Attack Boost Ability item. You will continue to unlock these upgrades for further detailed steps toward completion. Obtain Frieza Force Soldier, 20,000 Zeni, and Player Experience Points through trading. Zen-Oh's Orders possibly can give better rewards if Nappa's Proficiency is higher.
Now that you know How to complete Welcome to Frieza Force in Dragon Ball Sparking Zero, you can apply the guide and that's it.