Conditional logistic regression in SPSS (using multinomial logistic regression) and R (using clogistic() of Epi)

Conditional logistic regression in SPSS (using multinomial logistic
regression) and R (using clogistic() of Epi)

I want to use NOMREG of SPSS (by GUI from "Regression --> Multinomial
Logistic Regression") for my matched data. However, I don't know where to
insert the strata variable (the matching variable) into the GUI or syntax.
On a side note, I have a question on conditional logistic regression in R
that have posted it to the programming branch of the StackExchange because
the last time I sent a code-related question here, mods fried me (although
I see other people send their R code here). Anyways, the address for my R
question is this (LINK).