Create Permanent Association Between Two Tables

I've two tables in SQL Server 2014, in database named cnc

I wish to create a permanent association between the two tables, with referential integrity.  I cannot find, in all the books I've gone through, nor the websites I've visited, how to do this.

Table 1:
name: dbo.p
fields in table 1:
pID    autoenumerating, indexed
p_nm_l   varchar(25)
p_nm_f   varchar(25)

Table 2:
name: dbo.pe
fields in table 2:
pe_ID BigInt
pe_ssn1_
pe_ssn2_
pe_ssn3_
pe_dobm_
pe_dobd_
pe_doby_

I wish to associate - with a one to one - pID with pe_ID with pID as the primary field.  I've no clue how to do this.