Hi I need help to create a spanning tree for a report! my problem is how understand which the lowest bridge ID! I'm very n00b

So these are the results I have obtained, how should be the spanning tree?

Shakti
The root ID is: 8000.00:00:0c:76:4a:3e
Root path cost: 0
The bridgeID is: 8000.00:00:0c:76:4a:3e
Port ID: 8003

Agni
The root ID is: 8000.00:e0:b0:63:f5:58
Root path cost: 0
The bridgeID is: 8000.00:e0:b0:63:f5:58
Port ID: 8003

Yachi
The root ID is: 8000.00:10:7b:81:cd:68
Root path cost: 0
The bridgeID is: 8000.00:10:7b:81:cd:68
Port ID: 8002

Kenchi
The root ID is: 8000.00:03:e3:2a:4a:60
Root path cost: 0
The bridgeID is: 8000.00:03:
e3:2a:4a:60
Port ID: 8003

Vayu
The root ID is: 8000.00:00:0c:76:4a:3e
Root path cost: 0
The bridgeID is: 8000.00:00:0c:76:4a:3e
Port ID: 8002


Apah
The root ID is: 8000.00:00:0c:76:4a:3e
Root path cost: 0
The bridgeID is: 8000.00:00:0c:76:4a:3e
Port ID: 8002

Fenchi
The root ID is: 8000.00:e0:b0:63:f5:5
Root path cost: 0
The bridgeID is: 8000.00:e0:b0:63:f5:5
Port ID: 8002

Guchi
The root ID is: 8000.00:03:e3:2a:4a:60
Root path cost: 0
The bridgeID is: 8000.00:03:e3:2a:4a:60
Port ID: 8004

The lowest bridge ID is the one with the lowest (hexadecimal) address (assuming equal priority).

i know it... but how could i see which is the lowest hexadecimal number?

You write the address out in full, and leaving out the ':'. This will give you a hexadecimal number, for example, the digits of:
are
Just treat this as a number (with each digit in the range 0123456789ABCDEF meaning zero to fifteen), and compare them.

it is not clear the fact you added some zeros:

Could I do in this way?

Example
Shakti
The root ID is: 8000.00:00:0c:76:4a:3e

Agni
The root ID is: 8000.00:e0:b0:63:f5:58

Yachi
The root ID is: 8000.00:10:7b:81:cd:68

Kenchi
The root ID is: 8000.00:03:e3:2a:4a:60

Vayu
The root ID is: 8000.00:00:0c:76:4a:3e


Apah
The root ID is: 8000.00:00:0c:76:4a:3e


Fenchi
The root ID is: 8000.00:e0:b0:63:f5:5


Guchi
The root ID is: 8000.00:03:e3:2a:4a:60


So i could write

800000000c764a3e --- 9223372037063854000
800000e0b063f558 --- 9223373001886792000
800000107b81cd68 --- 9223372107646358000
80000003e32a4a60 --- 9223372053550877000
800000000c764a3e --- 9223372037063854000
800000000c764a3e --- 9223372037063854000
80000003e32a4a60 --- 9223372053550877000
80000003e32a4a60 --- 9223372053550877000

So kentchi is the root id!

Are right my reckons? and then, once i have the root ID, how could i build the spanning tree?

sorry, my mistake, i have fixed it in the post above

Yes, except the one you marked is not the smallest, and the ID you have for Fenchi is not right. Incidentally, you don't have to convert to decimal in order to do the comparison; just compare the numbers as you would in decimal from left to right.

You will have to know the path costs in order to build the rest of the tree (you have them all as zero, which doesn't seem right).