Access from the Eritrean side normally means arranging transport and permits through Asmara or Massawa, then travelling south toward the coastal lowlands. Independent wandering is not realistic here: roads are rough, settlements are sparse, and checkpoints can change what is possible.
The better-known tourist route to Dallol runs from Mekele in Ethiopia, but that does not help if you are travelling inside Eritrea. Check the political and security situation before building plans around this page.