How do you import textures the right way?

I tried importing a texture but the glow I have on the sprite (left side on the image) comes out as an outline (right side on the image). When I open the texture in Unreal sometimes it shows up as a glow sometimes as an outline. When I use it in a material, it always shows up as an outline.

I have 2 suggestions for you to try:
First, transparency functions better when using the .tga format instead of .png, so try importing as a .tga file first.

Second, set the material mode to translucency and see if that affects your outline.