To import a large mysql file to your database you need to first have SSH enabled on your account. This can be enable by submitting a support ticket requestiong this.
Once SSH is enabled on your account, you will need to place the mysql file into your file directory on your account.
Once this is done run a SSH program like Putty and connect to your account with your user details.
Once login enter the following in the command prompt:
mysql -u Database_USERNAME_here -p DATABASE_name_here < /home/username_here/public_html/mysql_file.sql
Enter the database password and wait until their is a response from the server. It may appear that nothing is happening but please be patient with this.