[Nexus 7 (2013) General] nhidog:
Alright let's see.

connect your device to your Mac

boot nexus7 into fastboot by holding Power + Volume Down

on your Mac, open a terminal, items in bold are the commands you need to issue

~ qdinh$ [B]mkdir helpme[/B]
~ qdinh$ [B]cd helpme[/B]
helpme qdinh$ [B]wget https://www.dropbox.com/sh/zt9gbvsafnaupls/5Ml2au5ji2/platform-tools-osx.zip[/B]
--2013-07-30 19:39:12-- https://www.dropbox.com/sh/zt9gbvsafnaupls/5Ml2au5ji2/platform-tools-osx.zip
Resolving www.dropbox.com... 199.47.216.170
Connecting to www.dropbox.com|199.47.216.170|:443... connected.
HTTP request sent, awaiting response... 302 FOUND
Location: https://dl.dropboxusercontent.com/sh/zt9gbvsafnaupls/5Ml2au5ji2/platform-tools-osx.zip?token_hash=AAEh8gskFVBgqcoswkN6Mcw-rB35VYupUy1zYbEoQ9j8Ww [following]
--2013-07-30 19:39:13-- https://dl.dropboxusercontent.com/sh/zt9gbvsafnaupls/5Ml2au5ji2/platform-tools-osx.zip?token_hash=AAEh8gskFVBgqcoswkN6Mcw-rB35VYupUy1zYbEoQ9j8Ww
Resolving dl.dropboxusercontent.com... 54.225.128.201
Connecting to dl.dropboxusercontent.com|54.225.128.201|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 10703816 (10M) [application/zip]
Saving to: ‘platform-tools-osx.zip’

100%[==========================================================================================================================================================>] 10,703,816 527KB/s in 23s

2013-07-30 19:39:38 (464 KB/s) - ‘platform-tools-osx.zip’ saved [10703816/10703816]

helpme qdinh$ [B]unzip platform-tools-osx.zip [/B]
Archive: platform-tools-osx.zip
inflating: platform-tools/NOTICE.txt
inflating: platform-tools/aapt
inflating: platform-tools/adb
inflating: platform-tools/aidl
creating: platform-tools/api/
inflating: platform-tools/dexdump
inflating: platform-tools/dx
inflating: platform-tools/fastboot
creating: platform-tools/lib/
inflating: platform-tools/llvm-rs-cc
creating: platform-tools/renderscript/
inflating: platform-tools/source.properties
helpme qdinh$ [B]cd platform-tools[/B]
platform-tools qdinh$ [B]./fastboot oem unlock[/B]
...
(bootloader) Unlocking bootloader...
(bootloader) erasing userdata...
(bootloader) erasing userdata done
(bootloader) erasing cache...
(bootloader) erasing cache done
(bootloader) Unlocking bootloader done!
OKAY [ 13.340s]
finished. total time: 13.340s

AT THIS POINT YOU SHOULD BE UNLOCKED, on nexus 7, use volumes button to select "START" system, POWER button to select choice, IMPORTANT LET IT FINISH BOOTING

Let's continue to download and flashing the TWRP

platform-tools qdinh$ [B]wget https://www.dropbox.com/sh/zt9gbvsafnaupls/Z7fsOLn8WP/nexus7TWRP.img[/B]
--2013-07-30 19:40:16-- https://www.dropbox.com/sh/zt9gbvsafnaupls/Z7fsOLn8WP/nexus7TWRP.img
Resolving www.dropbox.com... 199.47.216.170
Connecting to www.dropbox.com|199.47.216.170|:443... connected.
HTTP request sent, awaiting response... 302 FOUND
Location: https://dl.dropboxusercontent.com/sh/zt9gbvsafnaupls/Z7fsOLn8WP/nexus7TWRP.img?token_hash=AAEh8gskFVBgqcoswkN6Mcw-rB35VYupUy1zYbEoQ9j8Ww [following]
--2013-07-30 19:40:17-- https://dl.dropboxusercontent.com/sh/zt9gbvsafnaupls/Z7fsOLn8WP/nexus7TWRP.img?token_hash=AAEh8gskFVBgqcoswkN6Mcw-rB35VYupUy1zYbEoQ9j8Ww
Resolving dl.dropboxusercontent.com... 54.235.78.50
Connecting to dl.dropboxusercontent.com|54.235.78.50|:443... connected.
HTTP request sent, awaiting response... 200 OK
Length: 9842688 (9.4M) [application/octet-stream]
Saving to: ‘nexus7TWRP.img’

100%[==========================================================================================================================================================>] 9,842,688 453KB/s in 16s

2013-07-30 19:40:35 (620 KB/s) - ‘nexus7TWRP.img’ saved [9842688/9842688]

reboot nexus7 into bootloader (fastboot) again by holding Volume Down + Power

platform-tools qdinh$ [B]./fastboot flash recovery nexus7TWRP.img[/B]
sending 'recovery' (9612 KB)...
OKAY [ 0.438s]
writing 'recovery'...
OKAY [ 0.408s]
finished. total time: 0.846s
platform-tools qdinh$

boot nexus7 normally, I take you know how to download SuperSu.zip and place it on your device at this point to be flashed in TWRP