Welcome @a_malik
Please use the Custom Genome functions with tools. This will use reference data from your history. → Custom genome + custom build: How to use a genome that is not natively indexed at the server you are working at
You can load the data from the data provider of your choice. This is a guide about how to get the data (genome + annotation) from NCBI. → FAQ: NCBI reference data
More examples can be found under the tag custom-genome
We hope this helps! 