You need to have a .dat file in your directory containing the data required for filling the instance

for example : 

Ex1: You do have a parameter called cap in your model

and this parameter is defined over two sets called i,j where
i belongs to {0,1,2,3,4,5,6}

j belongs to {0,1,2,3,4,5,6}

model.cap = Param(model.i,model.j, within=Reals, mutable=True)

You just need to create a file with .dat extension and indicate the value for each combination of i and j (as a table) like this :

param cap      :  0 1  2 3 4 5 6  := 
                0 0 3  3 4 0 0 0
                1 0 0  0 0 2 0 0
                2 0 10 0 0 1 0 0 
                3 0 0  0 0 0 5 0 
                4 0 0  0 0 0 1 2
                5 0 0  0 0 0 0 5
                6 0 0  0 0 0 0 0;

This will feed the cap values as well as the sets i,j to the model

Ex2: You do have a parameter called N in your model

and this parameter is a constant number and has no set

model.N = Param(mutable=True)

You just need to create a file with .dat extension and indicate the value of N like this :

param N:=8;

Ex3: You do have a parameter called R over he set i in your model

i belongs to {0,1,2,3,4,5,6}

model.R = Param(model.i)

You just need to create a file with .dat extension and indicate the value of R for each element of i  like this :

param: i: 
           R:=
        1  2
        2  1.2
        3  1.8
        4  0.9
        5  3.2
        6  0.7;

This will feed the R values as well as the set i to the model