To submit a sequence to NCBI, there are two main tools that can be used: BankIt and Sequin. BankIt is a web-based tool for simple submissions like single sequences or small batches. Sequin is an offline software for more complex submissions. The submission process involves providing contact information, release date, reference information, organism name, sequence data, and annotating any features. Valid sequences must be at least 200 nucleotides long unless they are complete exons or non-coding RNA.