Hi, just follow the link

http://www.ncbi.nlm.nih.gov/blast/Blast.cgi?PROGRAM=blastx&PAGE_TYPE=BlastSearch&LINK_LOC=blasthome

and put you sequence in the empty square and press Blast button.

Hi,

you can submit your sequence via Bankit (BankIt can be used to submit both a single sequence and a set of sequences in one submission)

http://www.ncbi.nlm.nih.gov/WebSub/?tool=genbank

Good luck

You can use Sequin to submit your sequences in NCBI GenBank. Make a single .txt file for all the 300 sequences as per the guidelines, then open Sequin, fill the required details, upload the this file, save as the out put file and finally send this file to NCBI. 

Hi people, thanks for your help. I could submit using Sequin.

Thanks for all.

Cheers