Looks like a paved 2 lane road from Manaus on the river to the border. I’d think by ship up the river to that point. There’s a road coming in from the south but no bridge, just a ferry across at Manaus.
There’s an airport at Manaus that can handle jets. There’s also one at Boa Vista close to the Venezuela and Guyana borders with an 8800 foot runway. So close enough for air support.
Venezuela does appear to have some LSTs, so probably an attack from the sea on the coastal cities; the Brazilian navy doesn’t appear to have similar assets, but does appear to have the potential enemy out gunned and out subbed.
What should happen is the US and/or UK, need to drop in over Venezuela, in the dead of night and take out Maduro and his gang; no apologies - in and out. The pretext would be Maduro’s stated goal of annexing the territory (for which he’s already taken steps), in violation of an ICJ ruling. Then, dare any of his supporters (Russia, China, Iran), to do something about it. I imagine that most Venezuelans will be happy if the regime there is overthrown. Don’t know if this admin has the spine or ability to do any of this, however.