You can run the following from a command prompt to run SQL Server in the command prompt. First, change directories to the SQL server executables folder, (possibly C:\Program Files\Microsoft SQL Server\MSSQL\Binn).
sqlservr -f -s "SQL_INSTANCE"
Then, if you want to permanently change the tempdb location, your can run the following SQL:
ALTER DATABASE tempdb MODIFY FILE (NAME = tempdev, FILENAME = 'C:\<folders>\tempdb.mdf')
ALTER DATABASE tempdb MODIFY FILE (NAME = templog, FILENAME = 'C:\<folder>\templog.ldf')
Stop the SQL Server (control-c) in the command prompt and start the SQL Server service as normal.