Editing the portal

You can click inside the circles that are on the portal. A menu will pop and you can change the frame block, the inside block, the lighter and change a few other options.

Frame block

When you click at the top left of the portal, this menu will pop

You can choose the face of the block to be accepted (for example you can set a portal to only ignite if the (for example) acacia log is placed along the Y axis)

Then you can set the minimum portal size (minimum width x minimum height) and the maximum size (maximum width x maximum height)

After you are done with these optional changes you can choose a block from the list below or you can enter the block you want to use manually (If the editor does not have the block you entered, then it will use another image)

Inside block & Lighter material

When you click inside the circle at the portal's inside or at the lighter you will get a small box listing blocks & items that can be used. Similar to the frame block, you can input a block manually

Particles

When you click at the particle this box will appear

Here you can enable/disable the particles for the portal and you can also change the color of the particles.