Mitogenomes gap closure and making circular genome

Question

[KHURRAM SHAHZAD]

I am new in this field. I am doing complete assembly from Illumina paired-end sequencing. I have nuclear sequencing .fastq (R1 and R2) files from which I mapped with mitochondria reference genome and extract the mitochondrial sequences and assemble with getorganelle and spades. i get the scaffolds and contigs files from both of them. Now i want to do gap closure and to make it circular genome. Any one have simple idea to do it and how to validate the complete genome after making it circular? Thank you in advance