How to sign R API requests with credentials -

i'm trying use hackpad's api in r. unlike example in httr, hackpad documentation
1. uses oauth 1.0 and
2. says requests should signed credentials.

i not understand how 2nd part in r (with library). understand how use request, authorize, , access urls -- not provided hackpad (as far can tell).

here tried in r (to no success):

library(httr) myapp <- oauth_app("hackpad",                key = mykey,                secret = mysecret) hackpad_token <- oauth1.0_token(oauth_endpoint(authorize = 'https://hackpad.com/api/1.0/',                                            request = 'https://hackpad.com/api/1.0/',                                            access = 'https://hackpad.com/api/1.0/'),                             myapp) 

and also

req <- get("https://hackpad.com/api/1.0/pad/k9bpceeoo2q/content/latest.html",        config = authenticate(user=myuser,                              password=mypass)) 

which tries return api documentation content.

thank help