How do I make my flint and steel work?[SOLVED]

make and item and make a global trigger of when block right clicked with item 

then in there just place a soul fire block on x y+1 z and done

Make a new item for your custom flint and steel in Mcreator- under the 'triggers' tab, add a new procedure for 'when right clicked on block.'

In that procedure, first check that there is air in the space directly above the block. (Use an 'If' block from the flow control tab, and an 'is air at' block from the world tab. Replace the y value on the 'is air at block' with 'y + 1' to check the block above the target block.

Inside the if-block, put a 'place at' block from the 'block management' tab. Set the block to be placed to Soul Fire, and once again replace 'y' with 'y + 1.' (You can find the + and number blocks in the 'math' tab.) 

If you want to make it more specific/less buggy, you could also add a check that the block has a certain tag, (to make only specific blocks light on fire), check that the target face is solid, (so stuff like fences or slabs doesn't catch on fire), etc.