How to remove bubbles that exist on a vinyl decal?

Of course, it is better not to let the bubbles appear on the vinyl decal. If that happens, you need to do the following things.
You need to make sure where the bubbles are located. The bubbles could locate in a few different areas.
First, the bubbles could exist between the vinyl decal and the paper/plastic mask. This is not a big matter since paper/plastic mask is useless after you apply the vinyl decal. It will only be a problem if the bubbles prevent the paper/plastic mask to stick on the vinyl decal.
Second, the bubbles could exist on the side of vinyl decal on the applied area. If that is the case, you can squeeze out the bubbles one by one.
Third, the bubbles could exist in the center of vinyl decal on the applied area. If that is the case, it may be the worst situation. You may lose your vinyl decal if you cannot squeeze out the bubbles. To squeeze bubbles out of the vinyl decal, you need to push the bubbles to the side. If you cannot push the bubbles to the side, you can use a needle to release the air. It is better not to do so. You can also peel off the vinyl decal and apply it again. However, it is not a good idea either.
Again, it is better not to let the bubbles appear on the vinyl decal in your applied area. You may take more time to solve and fix the bubbles problems than apply the vinyl decal correctly in the first time.