WordNet sense 1 (a code (a series of characters or digits) that must be entered in some way (typed or dialed or spoken) to get the use of something (a telephone line or a computer or a local area network etc.)):

access code

WordNet sense 2 (the right to enter):

accession, admittance, entree, entrée

WordNet sense 3 ((computer science) the operation of reading or writing stored information):

memory access

WordNet sense 4 (a way of entering or leaving):

approach

WordNet sense 5 (reach or gain access to):

get at