1. Clone wallet sources
git clone https://github.com/Steve-sy/mmrcoinwallet.git
2. Modify CryptoNoteWallet.cmake
set(CN_PROJECT_NAME "mmrcoin-o")
set(CN_CURRENCY_DISPLAY_NAME "MMRcoin")
set(CN_CURRENCY_TICKER "MMR")
3. Set Alternative way is to create git submodule:
git submodule add https://github.com/Steve-sy/mmrcoin-o.git cryptonote
Replace URL with git remote repository of your coin.
4. Build
mkdir build && cd build && cmake .. && make