If you just wanted to see if a particular sequence was fungi, you could just use BLAST. If you had thousands of sequence reads from multiple unknown organisms,

If you just wanted to see if a particular sequence was fungi, you could just use BLAST. If you had thousands of sequence reads from multiple unknown organisms, then you’d have to implement a meta genomics pipeline. All the software for this is already made. You take your sequence reads, trim them a bit, assemble them into “contigs”, and then map those contigs to known genomes in the magical tree of life.