I have BSA powder and I have 1X PBS solution. How do I make 500 mls of
1%BSA in 1xPBS? Also how do I make 500 mls of 0.1%BSA in 1xPBS?
Teach me well how to calculate please. Is there a scientific simple
calculator online to help me with this?

What kind of percent are you talking about?  Mass to volume? molar?
volume to volume?

I think you mean mass to volume, as this is how these calculations are
commonly done.  Usually, percent denoted mass/volume.

To make 1% BSA in 500 mL PBS solution:

1. Pour 500 mL 1X PBS solution into beaker
2. Dissolve 5 grams of BSA powder into the solution.

If you want to be more exact (i.e. compensate for any volume change
with the addition of BSA powder), you can add the 5 grams of powder to
a smaller volume, and then top the volume off to 500 mL.  At this
concentration, you should have no solubility concerns.

Likewise, to make 0.1% BSA solution, just add 0.5 g BSA powder to 500 mL 1X PBS.