I'm going to be describing this process using Fedora, but any Linux that is using iscsiadm should use the same sort of configurations. To start off make sure you have the proper packages installed.

# yum install -y iscsi-initiator-utils 

Now you can easily see what iscsi targets are available on your portal (server):

# iscsiadm -m discovery -t st -p 10.20.0.2
10.20.0.2:3260,1 iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416
# iscsiadm -m node -l
Logging in to [iface: default, target: iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416, portal: 10.20.0.2,3260]
Login to [iface: default, target: iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416, portal: 10.20.0.2,3260]: successful

The first command will search for all targets available, the second will then login (-l) to all the found targets. If you only need to login to a specific target you can use the following:

# iscsiadm -m node --target "iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416" --portal "10.20.0.2:3260" -l
Logging in to [iface: default, target: iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416, portal: 10.20.0.2,3260]
Login to [iface: default, target: iqn.1986-03.com.sun:02:bf1479ba-a71d-c9d7-ab45-d51a1dca3416, portal: 10.20.0.2,3260]: successful

Once you have logged in to your target(s) you'll see them as a disk if you run fdisk -l:

# fdisk -l

Disk /dev/sdc: 214.7 GB, 214748364800 bytes
255 heads, 63 sectors/track, 26108 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xae668fde

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       26108   209712478+  8e  Linux LVM

I've already partitioned my target with fdisk but you may want to do the same. My primary use for iSCSI is to serve up a single large volume (zvol) and then I use LVM to give me volumes to use with my virtual machines.