I am looking to use the stat feature on my calc, can you assist ?

I have followed your description and entered bogus data in Lists L1, L2, and L3.
I hit STAT then CALC then Option 1, which is 1-Var Stats. In this context you have only one set of data. If the data set contains many repeated values you can enter the frequency for each (repeated) data item in List L2, inserting 1 if an item is not repeated.
Thus when you do 1-Var Statistics you have at most two Lists (L1 contains the data values, and L2 their frequencies).
If you press the 1-Var Stats calculation option, the calculator takes L1 as the default data list so you see List:L1 and the ALPHA cursor blinking
On the secoond line you see Frequency: and nothing else on the line.
On the third line you have Calculate.
If Your data is not in L1, you can change that by pressing the [2nd][2] (L2), or [2nd][3] (L3). Only one list is specified there, so no need for the comma to separate. (you are doing 1-var Stat).

If your frequency data is in L2 you must specify it on the line Frequency. However, since the ALPHA keyboard is activated you must deactivate it first by pressing the ALPHA key. After that press [2nd][2] to select L2 or [2nd][3] to specify L3
If there is no frequency list, leave the Line frequency empty.

Press STAT key. In the list of options that are displayed under the leftmost menu (EDIT) , press the 5:SetUpEditor. Press ENTER. It will restore the deleted list L1

Each "list" has to have a name. Usually, the lists are named L1, L2, L3, L4, L5, L6 ect. but you can give them text names as well.
To name the list, go to Stat--> Edit --> Input a name--> Enter To input a name, either do 2nd --> L1,L2,L3 ect.. or use Alpha --> Name

When you select 1-Var Stats, specify L2. If you don't specify a list, the calculator will assume L1.

You can recreate L1 by pressing
2ND [{] 1 STO 2ND [L1]

{ is on the ( key.
L1 is on the 1 key.

1. Press [STAT][5:SetUpEditor][ENTER].
2. Press [STAT][1:Edit..]
3. Enter your data in L1.
4. Press [STAT][CALC][1:1-Var Stats].
5. Command echoes on main screen.
6. If ONLY one list contains data, it must be L1.
7. When you do not specify the list in the command line it will take L1 by default.
8. If L1 is empty and the data is in L2, or another but L1, the name of list must be specified.
   

There is no L7 list. You can put your data in any available list. You can even create your own lists.
Anyway, to recover the L1,L2,L3, and L4,
Press [STAT][5:SetUpEdidor] [ENTER]
Calculator displays Done.

Press [STAT]. Under Menu EDIT, Press [1:Edit]
The List editor opens the L1,L2, etc. liststo let you enter your data.

Press Stat. Choose "set up editor" from this menu. You will be returned to the home screen. Press enter and you'll get the message "done". This should fix the problem.

try looking through this:
http://online.redwoods.cc.ca.us/instruct/kiyokoya/ExpReg/index.htm

also, you may find havina an algebra system on your omputer helpful a nice free one is Maxima:  http://wxmaxima.sourceforge.net/wiki/index.php/Main_Page

enter your data into L1 as x-coordinates and L2 as y-coordinates at (STAT) + (EDIT) and then turn on your StatPlot. Finally, press (STAT) ->(CALC) -> (4)LinReg(ax+b) and (L1) (,) (L2) (Y1)
nb: Y1 could be find from (VARS) -> (Y-VARS)->(1:Function...)

Here goes if you still need this...

STAT, EDIT, put information into L1 if only one variable stats, but put info into L1 and L2 if it is frequency table stats.

Then choose Stat, over to CALC, 1, enter...if 1 variable stats then press enter again. If frequency table stats, then choose STAT, over to CALC, 1, 2nd, 1 [L!], 2nd, 2 [L2], enter.