How do I do a manual fsck?

My pc doesn't want to start saying:

/dev/mmcblk0p2p cointais a file system with errors, check forced. Inodes that were part of a corrupted orphan linked list found. /dev/mmcblk0p2: UNEXPECTED INCONSISTENCY; RUN fsck MANUALLY. (i.e., without -a or -p options) fsck exited with status code 4 The root filesystem on /dev/mmcblk0p2 requires a manual fsck BusyBox v1.22.1 (Ubuntu 1:1.22.0-15ubuntu1) built-in shell (ash) Enter 'help' for a list of built-in commands.

What do I do?